Negative ion beam source vacuum method and apparatus used in conjunction with a charged particle cancer therapy system

ABSTRACT

The invention comprises a negative ion beam source vacuum method and apparatus used as part of an ion beam injection system, which is used in conjunction with multi-axis charged particle or proton beam radiation therapy of cancerous tumors. The negative ion beam source contains a vacuum chamber isolated by a vacuum barrier from the vacuum tube of the synchrotron. The negative ion beam source vacuum system preferably includes: a first pump turbo molecular pump, a large holding volume, and a semi-continuously operating pump. By only pumping ion beam source vacuum chamber and by only semi-continuously operating the ion beam source vacuum based on sensor readings about the holding volume, the lifetime of the semi-continuously operating pump is extended.

CROSS REFERENCES TO RELATED APPLICATIONS

This application:

-   -   is a continuation-in-part of U.S. patent application Ser. No.        12/425,683 filed Apr. 17, 2009 now U.S. Pat. No. 7,939,809,        which claims the benefit of:        -   U.S. provisional patent application No. 61/055,395 filed May            22, 2008;        -   U.S. provisional patent application No. 61/137,574 filed            Aug. 1, 2008;        -   U.S. provisional patent application No. 61/192,245 filed            Sep. 17, 2008;        -   U.S. provisional patent application No. 61/055,409 filed May            22, 2008;        -   U.S. provisional patent application No. 61/203,308 filed            Dec. 22, 2008;        -   U.S. provisional patent application No. 61/188,407 filed            Aug. 11, 2008;        -   U.S. provisional patent application No. 61/188,406 filed            Aug. 11, 2008;        -   U.S. provisional patent application No. 61/189,815 filed            Aug. 25, 2008;        -   U.S. provisional patent application No. 61/201,731 filed            Dec. 15, 2008;        -   U.S. provisional patent application No. 61/205,362 filed            Jan. 21, 2009;        -   U.S. provisional patent application No. 61/134,717 filed            Jul. 14, 2008;        -   U.S. provisional patent application No. 61/134,707 filed            Jul. 14, 2008;        -   U.S. provisional patent application No. 61/201,732 filed            Dec. 15, 2008;        -   U.S. provisional patent application No. 61/198,509 filed            Nov. 7, 2008;        -   U.S. provisional patent application No. 61/134,718 filed            Jul. 14, 2008;        -   U.S. provisional patent application No. 61/190,613 filed            Sep. 2, 2008;        -   U.S. provisional patent application No. 61/191,043 filed            Sep. 8, 2008;        -   U.S. provisional patent application No. 61/192,237 filed            Sep. 17, 2008;        -   U.S. provisional patent application No. 61/201,728 filed            Dec. 15, 2008;        -   U.S. provisional patent application No. 61/190,546 filed            Sep. 2, 2008;        -   U.S. provisional patent application No. 61/189,017 filed            Aug. 15, 2008;        -   U.S. provisional patent application No. 61/198,248 filed            Nov. 5, 2008;        -   U.S. provisional patent application No. 61/198,508 filed            Nov. 7, 2008;        -   U.S. provisional patent application No. 61/197,971 filed            Nov. 3, 2008;        -   U.S. provisional patent application No. 61/199,405 filed            Nov. 17, 2008;        -   U.S. provisional patent application No. 61/199,403 filed            Nov. 17, 2008; and        -   U.S. provisional patent application No. 61/199,404 filed            Nov. 17, 2008;    -   claims the benefit of U.S. provisional patent application No.        61/209,529 filed Mar. 9, 2009;    -   claims the benefit of U.S. provisional patent application No.        61/208,182 filed Feb. 23, 2009;    -   claims the benefit of U.S. provisional patent application No.        61/208,971 filed Mar. 3, 2009;    -   claims the benefit of U.S. provisional patent application No.        61/270,298, filed Jul. 7, 2009; and    -   claims priority to PCT patent application serial No.:        PCT/RU2009/00015, filed Mar. 4, 2009,    -   all of which are incorporated herein in their entirety by this        reference thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to treatment of solid cancers. Moreparticularly, the invention relates to an negative ion beam sourcevacuum system used as part of a ion beam injection system, which is usedin conjunction with charged particle cancer therapy beam acceleration,extraction, and/or targeting methods and apparatus.

2. Discussion of the Prior Art

Cancer Treatment

Proton therapy systems typically include: a beam generator, anaccelerator, and a beam transport system to move the resultingaccelerated protons to a plurality of treatment rooms where the protonsare delivered to a tumor in a patient's body.

Proton therapy works by aiming energetic ionizing particles, such asprotons accelerated with a particle accelerator, onto a target tumor.These particles damage the DNA of cells, ultimately causing their death.Cancerous cells, because of their high rate of division and theirreduced ability to repair damaged DNA, are particularly vulnerable toattack on their DNA.

Due to their relatively enormous size, protons scatter less easily inthe tissue and there is very little lateral dispersion. Hence, theproton beam stays focused on the tumor shape without much lateral damageto surrounding tissue. All protons of a given energy have a certainrange, defined by the Bragg peak, and the dosage delivery to tissueratio is maximum over just the last few millimeters of the particle'srange. The penetration depth depends on the energy of the particles,which is directly related to the speed to which the particles wereaccelerated by the proton accelerator. The speed of the proton isadjustable to the maximum rating of the accelerator. It is thereforepossible to focus the cell damage due to the proton beam at the verydepth in the tissues where the tumor is situated. Tissues situatedbefore the Bragg peak receive some reduced dose and tissues situatedafter the peak receive none.

Patents related to the current invention are summarized here.

Proton Beam Therapy System

F. Cole, et. al. of Loma Linda University Medical Center “Multi-StationProton Beam Therapy System”, U.S. Pat. No. 4,870,287 (Sep. 26, 1989)describe a proton beam therapy system for selectively generating andtransporting proton beams from a single proton source and accelerator toa selected treatment room of a plurality of patient treatment rooms.

Accelerator/Synchrotron

H. Tanaka, et. al. “Charged Particle Accelerator”, U.S. Pat. No.7,259,529 (Aug. 21, 2007) describe a charged particle accelerator havinga two period acceleration process with a fixed magnetic field applied inthe first period and a timed second acceleration period to providecompact and high power acceleration of the charged particles.

V. Kulish, et. al. “Inductional Undulative EH-Accelerator”, U.S. Pat.No. 6,433,494 (Aug. 13, 2002) describe an inductive undulativeEH-accelerator for acceleration of beams of charged particles. Thedevice consists of an electromagnet undulation system, whose drivingsystem for electromagnets is made in the form of a radio-frequency (RF)oscillator operating in the frequency range from about 100 KHz to 10GHz.

K. Saito, et. al. “Radio-Frequency Accelerating System and Ring TypeAccelerator Provided with the Same”, U.S. Pat. No. 5,917,293 (Jun. 29,1999) describe a radio-frequency accelerating system having a loopantenna coupled to a magnetic core group and impedance adjusting meansconnected to the loop antenna. A relatively low voltage is applied tothe impedance adjusting means allowing small construction of theadjusting means.

J. Hirota, et. al. “Ion Beam Accelerating Device Having SeparatelyExcited Magnetic Cores”, U.S. Pat. No. 5,661,366 (Aug. 26, 1997)describe an ion beam accelerating device having a plurality of highfrequency magnetic field inducing units and magnetic cores.

J. Hirota, et. al. “Acceleration Device for Charged Particles”, U.S.Pat. No. 5,168,241 (Dec. 1, 1992) describe an acceleration cavity havinga high frequency power source and a looped conductor operating under acontrol that combine to control a coupling constant and/or de-tuningallowing transmission of power more efficiently to the particles.

Vacuum Chamber

T. Kobari, et. al. “Apparatus For Treating the Inner Surface of VacuumChamber”, U.S. Pat. No. 5,820,320 (Oct. 13, 1998) and T. Kobari, et. al.“Process and Apparatus for Treating Inner Surface Treatment of Chamberand Vacuum Chamber”, U.S. Pat. No. 5,626,682 (May 6, 1997) both describean apparatus for treating an inner surface of a vacuum chamber includingmeans for supplying an inert gas or nitrogen to a surface of the vacuumchamber with a broach. Alternatively, the broach is used for supplying alower alcohol to the vacuum chamber for dissolving contaminants on thesurface of the vacuum chamber.

Intensity

H. Akiyama, et. al. “Charged-Particle Beam Irradiation Method andSystem”, U.S. Pat. No. 6,433,349 (Aug. 13, 2002) and H. Akiyama, et. al.“Charged-Particle Beam Irradiation Method and System”, U.S. Pat. No.6,265,837 (Jul. 24, 2001) both describe a charged particle beamirradiation system that includes a changer for changing energy of theparticle and an intensity controller for controlling an intensity of thecharged-particle beam.

Problem

There exists in the art of particle beam therapy of cancerous tumors aneed for efficiently operating a negative ion beam source vacuum system.There further exists in the art a need for extracting the negative ion,focusing the negative ion, converting the negative ion into a positiveion, and injecting the positive ion into a synchrotron. There furtherexists in the art of particle beam treatment of cancerous tumors in thebody a need for reduced synchrotron power supply requirements, reducedsynchrotron size, and control of synchrotron magnetic fields. Stillfurther, there exists a need in the art to control the charged particlecancer therapy system in terms of specified energy, intensity, and/ortiming of charged particle delivery. Yet still further, there exists aneed for efficient, precise, and/or accurate noninvasive, in-vivotreatment of a solid cancerous tumor with minimization of damage tosurrounding healthy tissue in a patient.

SUMMARY OF THE INVENTION

The invention comprises a negative ion beam source vacuum method andapparatus used as part of an ion beam injection system, which is part ofa charged particle cancer therapy beam system.

DESCRIPTION OF THE FIGURES

FIG. 1 illustrates component connections of a particle beam therapysystem;

FIG. 2 illustrates a charged particle therapy system;

FIG. 3 illustrates an ion beam generation system;

FIG. 4 illustrates a negative ion beam source;

FIG. 5 illustrates an ion beam focusing system;

FIGS. 6 A-D illustrate electrodes about a negative ion beam path;

FIG. 7 illustrates a negative ion beam path vacuum system;

FIG. 8 is a synchrotron control flowchart;

FIG. 9 illustrates straight and turning sections of a synchrotron

FIG. 10 illustrates bending magnets of a synchrotron;

FIG. 11 provides a perspective view of a bending magnet;

FIG. 12 illustrates a cross-sectional view of a bending magnet;

FIG. 13 illustrates a cross-sectional view of a bending magnet;

FIG. 14 illustrates magnetic field concentration in a bending magnet;

FIG. 15 illustrates correction coils in a bending magnet;

FIG. 16 illustrates a magnetic turning section of a synchrotron;

FIG. 17 illustrates a magnetic field control system;

FIG. 18 illustrates a charged particle extraction and intensity controlsystem;

FIG. 19 illustrates a patient positioning system from: (A) a front viewand (B) a top view;

FIG. 20 illustrates multi-dimensional scanning of a charged particlebeam spot scanning system operating on: (A) a 2-D slice or (B) a 3-Dvolume of a tumor;

FIG. 21 illustrates an electron gun source used in generating X-rayscoupled with a particle beam therapy system;

FIG. 22 illustrates an X-ray source proximate a particle beam path;

FIG. 23 illustrates an expanded X-ray beam path;

FIG. 24 provides an example of a patient positioning system;

FIG. 25 illustrates a head restraint system; and

FIG. 26 illustrates hand and head supports.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates generally to treatment of solid cancers. Moreparticularly, the invention relates to a negative ion source vacuumsystem as part of an ion beam injection system used in conjunction withcharged particle cancer therapy beam injection, acceleration,extraction, and/or targeting methods and apparatus.

Novel design features of a synchrotron are described. Particularly, anegative ion beam source with novel features in the negative ion source,ion source vacuum system, ion beam focusing lens, and tandem acceleratorare described. Additionally, turning magnets, edge focusing magnets,magnetic field concentration magnets, winding and correction coils, flatmagnetic field incident surfaces, and extraction elements are describedthat minimize the overall size of the synchrotron, provide a tightlycontrolled proton beam, directly reduce the size of required magneticfields, directly reduce required operating power, and allow continualacceleration of protons in a synchrotron even during a process ofextracting protons from the synchrotron. The ion beam source system andsynchrotron are preferably computer integrated with a patient imagingsystem and a patient interface including breath monitoring sensors andpatient positioning elements.

Used in conjunction with the injection vacuum system, an imaging system,breathing sensors, and novel features of a synchrotron are described.Particularly, intensity control of a charged particle beam acceleration,extraction, and/or targeting method and apparatus used in conjunctionwith charged particle beam radiation therapy of cancerous tumors aredescribed. More particularly, intensity and energy control of a chargedparticle stream of a synchrotron is described where the synchrotronincludes any of: turning magnets, edge focusing magnets, concentratingmagnetic field magnets, winding and control coils, and extractionelements. The synchrotron control elements allow tight control of thecharged particle beam, which compliments the tight control of patientpositioning to yield efficient treatment of a solid tumor with reducedtissue damage to surrounding healthy tissue. In addition, the systemreduces the overall size of the synchrotron, provides a tightlycontrolled proton beam, directly reduces the size of required magneticfields, directly reduces required operating power, and allows continualacceleration of protons in a synchrotron even during a process ofextracting protons from the synchrotron.

Charged Particle Beam Therapy

Throughout this document, a charged particle beam therapy system, suchas a proton beam, hydrogen ion beam, or carbon ion beam, is described.Herein, the charged particle beam therapy system is described using aproton beam. However, the aspects taught and described in terms of aproton beam are not intended to be limiting to that of a proton beam andare illustrative of a charged particle beam system. Any of thetechniques described herein are equally applicable to any chargedparticle beam system.

Referring now to FIG. 1, a charged particle beam system 100 isillustrated. The charged particle beam preferably comprises a number ofsubsystems including any of: a main controller 110; an injection system120; a synchrotron 130 that typically includes: (1) an acceleratorsystem 132 and (2) an extraction system 134; ascanning/targeting/delivery system 140; a patient interface module 150;a display system 160; and/or an imaging system 170.

An exemplary method of use of the charged particle beam system 100 isprovided. The main controller 110 controls one or more of the subsystemsto accurately and precisely deliver protons to a tumor of a patient. Forexample, the main controller 110 obtains an image, such as a portion ofa body and/or of a tumor, from the imaging system 170. The maincontroller 110 also obtains position and/or timing information from thepatient interface module 150. The main controller 110 then optionallycontrols the injection system 120 to inject a proton into a synchrotron130. The synchrotron typically contains at least an accelerator system132 and an extraction system 134. The main controller preferablycontrols the proton beam within the accelerator system, such as bycontrolling speed, trajectory, and timing of the proton beam. The maincontroller then controls extraction of a proton beam from theaccelerator through the extraction system 134. For example, thecontroller controls timing, energy, and/or intensity of the extractedbeam. The controller 110 also preferably controls targeting of theproton beam through the scanning/targeting/delivery system 140 to thepatient interface module 150. One or more components of the patientinterface module 150 are preferably controlled by the main controller110. Further, display elements of the display system 160 are preferablycontrolled via the main controller 110. Displays, such as displayscreens, are typically provided to one or more operators and/or to oneor more patients. In one embodiment, the main controller 110 times thedelivery of the proton beam from all systems, such that protons aredelivered in an optimal therapeutic manner to the patient.

Herein, the main controller 110 refers to a single system controllingthe charged particle beam system 100, to a single controller controllinga plurality of subsystems controlling the charged particle beam system100, or to a plurality of individual controllers controlling one or moresub-systems of the charged particle beam system 100.

Synchrotron

Herein, the term synchrotron is used to refer to a system maintainingthe charged particle beam in a circulating path. Further, the chargedparticle beam is referred to herein as circulating along a circulatingpath about a central point of the synchrotron. The circulating path isalternatively referred to as an orbiting path; however, the orbitingpath does not refer to a perfect circle or ellipse, rather it refers tocycling of the protons around a central point or region.

Referring now to FIG. 2, an illustrative exemplary embodiment of oneversion of the charged particle beam system 100 is provided. The number,position, and described type of components is illustrative andnon-limiting in nature. In the illustrated embodiment, an injectorsystem 120 or ion source or charged particle beam source generatesprotons. The protons are delivered into a vacuum tube that runs into,through, and out of the synchrotron. The generated protons are deliveredalong an initial path 262. Focusing magnets 230, such as quadrupolemagnets or injection quadrupole magnets, are used to focus the protonbeam path. A quadrupole magnet is a focusing magnet. An injector bendingmagnet 232 bends the proton beam toward the plane of the synchrotron130. The focused protons having an initial energy are introduced into aninjector magnet 240, which is preferably an injection Lamberson magnet.Typically, the initial beam path 262 is along an axis off of, such asabove, a circulating plane of the synchrotron 130. The injector bendingmagnet 232 and injector magnet 240 combine to move the protons into thesynchrotron 130. Main turning magnets 250, bending magnets, or dipolemagnets or circulating magnets are used to turn the protons along acirculating beam path 264. A dipole magnet is a bending magnet. The mainbending magnets 250 bend the initial beam path 262 into a circulatingbeam path 264. In this example, the main bending magnets 250 orcirculating magnets are represented as four sets of four magnets tomaintain the circulating beam path 264 into a stable circulating beampath. However, any number of magnets or sets of magnets are optionallyused to move the protons around a single orbit in the circulationprocess. The protons pass through an accelerator 270. The acceleratoraccelerates the protons in the circulating beam path 264. As the protonsare accelerated, the fields applied by the magnets are increased.Particularly, the speed of the protons achieved by the accelerator 270are synchronized with magnetic fields of the main bending magnets 250 orcirculating magnets to maintain stable circulation of the protons abouta central point or region 280 of the synchrotron. At separate points intime the accelerator 270/main bending magnet 250 combination is used toaccelerate and/or decelerate the circulating protons while maintainingthe protons in the circulating path or orbit. An extraction element ofthe inflector/deflector system 290 is used in combination with aLamberson extraction magnet 292 to remove protons from their circulatingbeam path 264 within the synchrotron 130. One example of a deflectorcomponent is a Lamberson magnet. Typically the deflector moves theprotons from the circulating plane to an axis off of the circulatingplane, such as above the circulating plane. Extracted protons arepreferably directed and/or focused using an extraction bending magnet237 and extraction focusing magnets 235, such as quadrupole magnetsalong a transport path 268 into the scanning/targeting/delivery system140. Two components of a scanning system 140 or targeting systemtypically include a first axis control 142, such as a vertical control,and a second axis control 144, such as a horizontal control. A nozzlesystem 146 is used for imaging the proton beam and/or as a vacuumbarrier between the low pressure beam path of the synchrotron and theatmosphere. Protons are delivered with control to the patient interfacemodule 150 and to a tumor of a patient. All of the above listed elementsare optional and may be used in various permutations and combinations.

Ion Beam Generation System

An ion beam generation system generates a negative ion beam, such as ahydrogen anion or H⁻ beam; preferably focuses the negative ion beam;converts the negative ion beam to a positive ion beam, such as a protonor H⁺ beam; and injects the positive ion beam into the synchrotron 130.Portions of the ion beam path are preferably under partial vacuum. Eachof these systems are further described, infra.

Referring now to FIG. 3, an exemplary ion beam generation system 300 isillustrated. As illustrated, the ion beam generation system 300 has fourmajor elements: a negative ion source 310, a first partial vacuum system330, an optional ion beam focusing system 350, and a tandem accelerator390.

Still referring to FIG. 3, the negative ion source 310 preferablyincludes an inlet port 312 for injection of hydrogen gas into a hightemperature plasma chamber 314. In one embodiment, the plasma chamberincludes a magnetic material 316, which provides a magnetic fieldbarrier 317 between the high temperature plasma chamber 314 and a lowtemperature plasma region on the opposite side of the magnetic fieldbarrier. An extraction pulse is applied to a negative ion extractionelectrode 318 to pull the negative ion beam into a negative ion beampath 319, which proceeds through the first partial vacuum system 330,through the ion beam focusing system 350, and into the tandemaccelerator 390.

Still referring to FIG. 3, the first partial vacuum system 330preferably includes: a first pump 332, such as a continuously operatingpump and/or a turbo molecular pump; a large holding volume 334; and asemi-continuously operating pump 336. Preferably, a pump controller 340receives a signal from a pressure sensor 342 monitoring pressure in thelarge holding volume 334. Upon a signal representative of a sufficientpressure in the large holding volume 334, the pump controller 340instructs an actuator 345 to open a valve 346 between the large holdingvolume and the semi-continuously operating pump 336 and instructs thesemi-continuously operating pump to turn on and pump to atmosphereresidual gases out of the vacuum line 320 about the charged particlestream. In this fashion, the lifetime of the semi-continuously operatingpump is extended by only operating semi-continuously and as needed.

Still referring to FIG. 3, the ion beam focusing system 350 includes twoor more electrodes where one electrode of each electrode pair partiallyobstructs the ion beam path with conductive paths 372, such as aconductive mesh. In the illustrated example, three ion beam focusingsystem sections are illustrated, a two electrode ion focusing section360 and a three electrode ion focusing section 370. In a given electrodepair, electric field lines, running between the conductive mesh of afirst electrode and a second electrode, provide inward forces focusingthe negative ion beam. Multiple such electrode pairs provide multiplenegative ion beam focusing regions. Preferably the two electrode ionfocusing section 360, first three electrode ion focusing section 370,and a second three electrode ion focusing section are placed after thenegative ion source and before the tandem accelerator and/or cover aspace of about 0.5, 1, or 2 meters along the ion beam path 319. Ion beamfocusing systems are further described, infra.

Still referring to FIG. 3, the tandem accelerator 390 preferablyincludes a foil 395 or converting foil, such as a carbon foil. Thenegative ions in the negative ion beam path 319 are converted topositive ions, such as protons, and the initial ion beam path 262results. The foil 395 is preferably sealed directly or indirectly to theedges of the vacuum tube 320 providing for a higher pressure, such asabout 10⁻⁵ torr, to be maintained on the side of the foil 395 having thenegative ion beam path 319 and a lower pressure, such as about 10⁻⁷torr, to be maintained on the side of the foil 390 having the proton ionbeam path 262. Having the foil 395 physically separating the vacuumchamber 320 into two pressure regions allows for a system having fewerand/or smaller pumps to maintain the lower pressure system in thesynchrotron 130 as the inlet hydrogen and its residuals are extracted ina separate contained and isolated space by the first partial vacuumsystem 330.

Negative Ion Source

An example of the negative ion source 310 is further described herein.Referring now to FIG. 4, a cross-section of an exemplary negative ionsource system 400 is provided. The negative ion beam 319 is created inmultiple stages. During a first stage, hydrogen gas is injected into achamber. During a second stage, a negative ion is created by applicationof a first high voltage pulse, which creates a plasma about the hydrogengas to create negative ions. During a third stage, a magnetic fieldfilter is applied to components of the plasma. During a fourth stage,the negative ions are extracted from a low temperature plasma region, onthe opposite side of the magnetic field barrier, by application of asecond high voltage pulse. Each of the four stages are furtherdescribed, infra. While the chamber is illustrated as a cross-section ofa cylinder, the cylinder is exemplary only and any geometry applies tothe magnetic loop containment walls, described infra.

In the first stage, hydrogen gas is injected through an inlet port 442into a high temperature plasma region 490. The injection port 442 isopen for a short period of time, such as less than about 1, 5, or 10microseconds to minimize vacuum pump requirements to maintain vacuumchamber 320 requirements. The high temperature plasma region ismaintained at reduced pressure by the partial vacuum system 330. Theinjection of the hydrogen gas is optionally controlled by the maincontroller 110, which is responsive to imaging system 170 informationand patient interface module 150 information, such as patientpositioning and period in a respiration cycle.

In the second stage, a high temperature plasma region is created byapplying a first high voltage pulse across a first electrode 422 and asecond electrode 424. For example a 5 kV pulse is applied for about 20microseconds with 5 kV at the second electrode 424 and about 0 kVapplied at the first electrode 422. Hydrogen in the chamber is broken,in the high temperature plasma region 490, into component parts, such asany of: atomic hydrogen, H⁰, a proton, H⁺, an electron, e⁻, a hydrogenanion, and H⁻.

In the third stage, the high temperature plasma region 490 is at leastpartially separated from a low temperature plasma region 492 by amagnetic field or magnetic field barrier 430. High energy electrons arerestricted from passing through the magnetic field barrier 430. In thismanner, the magnetic field barrier 430 acts as a filter between, zone Aand zone B, in the negative ion source. Preferably, a central magneticmaterial 410 is placed within the high temperature plasma region 490,such as along a central axis of the high temperature plasma region 490.Preferably, the first electrode 422 and second electrode 424 arecomposed of magnetic materials, such as iron. Preferably, the outerwalls 450 of the high temperature plasma region, such as cylinder walls,are composed of a magnetic material, such as a permanent magnet, ferric,or iron based material, or a ferrite dielectric ring magnet. In thismanner a magnetic field loop is created by: the central magneticmaterial 410, first electrode 422, the outer walls 450, the secondelectrode 424, and the magnetic field barrier 430. Again, the magneticfield barrier 430 restricts high energy electrons from passing throughthe magnetic field barrier 430. Low energy electrons interact withatomic hydrogen, H⁰, to create a hydrogen anion, H⁻, in the lowtemperature plasma region 492.

In the fourth stage, a second high voltage pulse or extraction pulse isapplied at a third electrode 426. The second high voltage pulse ispreferentially applied during the later period of application of thefirst high voltage pulse. For example, an extraction pulse of about 25kV is applied for about the last 5 microseconds of the first creationpulse of about 20 microseconds. The potential difference, of about 20kV, between the third electrode 426 and second electrode 424 extractsthe negative ion, H⁻, from the low temperature plasma region 492 andinitiates the negative ion beam 390, from zone B to zone C.

The magnetic field barrier 430 is optionally created in number of ways.An example of creation of the magnetic field barrier 430 using coils isprovided. In this example, the elements described, supra, in relation toFIG. 4 are maintained with several differences. First, the magneticfield is created using coils. An isolating material is preferablyprovided between the first electrode 422 and the cylinder walls 450 aswell as between the second electrode 424 and the cylinder walls 450. Thecentral material 410 and/or cylinder walls 450 are optionally metallic.In this manner, the coils create a magnetic field loop through the firstelectrode 422, isolating material, outer walls 450, second electrode424, magnetic field barrier 430, and the central material 410.Essentially, the coils generate a magnetic field in place of productionof the magnetic field by the magnetic material 410. The magnetic fieldbarrier 430 operates as described, supra. Generally, any manner thatcreates the magnetic field barrier 430 between the high temperatureplasma region 490 and low temperature plasma region 492 is functionallyapplicable to the ion beam extraction system 400.

Ion Beam Focusing System

Referring now to FIG. 5, the ion beam focusing system 350 is furtherdescribed. In this example, three electrodes are used. In this example,the first electrode 510 and third electrode 530 are both negativelycharged and each is a ring electrode circumferentially enclosing or atleast partially enclosing the negative ion beam path 319. The secondelectrode 520 is positively charged and is also a ring electrodecircumferentially enclosing the negative ion beam path. In addition, thesecond electrode includes one or more conducting paths 372 runningthrough the negative ion beam path 319. For example, the conductingpaths are a wire mesh, a conducting grid, or a series of substantiallyparallel conducting lines running across the second electrode. In use,electric field lines run from the conducting paths of the positivelycharged electrode to the negatively charged electrodes. For example, inuse the electric field lines 540 run from the conducting paths 372 inthe negative ion beam path 319 to the negatively charged electrodes 510,530. Two ray trace lines 550, 560 of the negative ion beam path are usedto illustrate focusing forces. In the first ray trace line 550, thenegative ion beam encounters a first electric field line at point M.Negatively charged ions in the negative ion beam 550 encounter forcesrunning up the electric field line 571, illustrated with an x-axiscomponent vector 572. The x-axis component force vectors 572 alters thetrajectory of the first ray trace line to a inward focused vector 552,which encounters a second electric field line at point N. Again, thenegative ion beam 552 encounters forces running up the electric fieldline 573, illustrated as having an inward force vector with an x-axiscomponent 574, which alters the inward focused vector 552 to a moreinward focused vector 554. Similarly, in the second ray trace line 560,the negative ion beam encounters a first electric field line at point O.Negatively charged ions in the negative ion beam encounter forcesrunning up the electric field line 575, illustrated as having a forcevector with an x-axis force 576. The inward force vectors 576 alters thetrajectory of the second ray trace line 560 to an inward focused vector562, which encounters a second electric field line at point P. Again,the negative ion beam encounters forces running up the electric fieldline 577, illustrated as having force vector with an x-axis component578, which alters the inward focused vector 562 to a more inward focusedvector 564. The net result is a focusing effect on the negative ionbeam. Each of the force vectors 572, 574, 576, 578 optionally has xand/or y force vector components resulting in a 3-dimensional focusingof the negative ion beam path. Naturally, the force vectors areillustrative in nature, many electric field lines are encountered, andthe focusing effect is observed at each encounter resulting in integralfocusing. The example is used to illustrate the focusing effect.

Still referring to FIG. 5, optionally any number of electrodes are used,such as 2, 3, 4, 5, 6, 7, 8, or 9 electrodes, to focus the negative ionbeam path where every other electrode, in a given focusing section, iseither positively or negatively charged. For example, three focusingsections are optionally used. In the first ion focusing section 360, apair of electrodes are used where the first electrode encountered alongthe negative ion beam path is negatively charged and the secondelectrode is positively charged, resulting in focusing of the negativeion beam path. In the second ion focusing section 370, two pairs ofelectrodes are used, where a common positively charged electrode with aconductive mesh running through the negatively ion beam path 319 isused. Thus, in the second ion focusing section 370, the first electrodeencountered along the negative ion beam path is negatively charged andthe second electrode is positively charged, resulting in focusing of thenegative ion beam path. Further, in the second ion focusing section,moving along the negative ion beam path, a second focusing effect isobserved between the second positively charged electrode and a thirdnegatively charged electrode. In this example, a third ion focusingsection is used that again has three electrodes, which acts in thefashion of the second ion focusing section, describe supra.

Referring now to FIG. 6, the central regions of the electrodes in theion beam focusing system 350 are further described. Referring now toFIG. 6A, the central region of the negatively charged ring electrode 510is preferably void of conductive material. Referring now to FIGS. 6B-D,the central region of positively charged electrode ring 520 preferablycontains conductive paths 372. Preferably, the conductive paths 372 orconductive material within the positively charged electrode ring 520blocks about 1, 2, 5, or 10 percent of the area and more preferablyblocks about 5 percent of the cross-sectional area of the negative ionbeam path 319. Referring now to FIG. 6B, one option is a conductive mesh610. Referring now to FIG. 6C, a second option is a series of conductivelines 620 running substantially in parallel across the positivelycharged electrode ring 520 that surrounds a portion of the negative ionbeam path 319. Referring now to FIG. 6D, a third option is to have afoil 630 or metallic layer cover all of the cross-sectional area of thenegative ion beam path with holes punched through the material, wherethe holes take up about 90-99 percent and more preferably about 95percent of the area of the foil. More generally, the pair of electrodesare configure to provide electric field lines that provide focusingforce vectors to the negative ion beam when the ions in the negative ionbeam translate through the electric field lines, as described supra.

In an example of a two electrode negative beam ion focusing systemhaving a first cross-sectional diameter, d₁, the negative ions arefocused using the two electrode system to a second cross-sectionaldiameter, d₂, where d₁>d₂. Similarly, in an example of a three electrodenegative beam ion focusing system having a first cross-sectionaldiameter, d₁, the negative ions are focused using the three electrodesystem to a third cross-sectional diameter, d₃, where d₁>d₃. For likepotentials on the electrodes, the three electrode system providestighter or stronger focusing compared to the two-electrode system,d₃<d₂.

In the examples provided, supra, of a multi-electrode ion beam focusingsystem, the electrodes are rings. More generally, the electrodes are ofany geometry sufficient to provide electric field lines that providefocusing force vectors to the negative ion beam when the ions in thenegative ion beam translate through the electric field lines, asdescribed supra. For example, one negative ring electrode is optionallyreplaced by a number of negatively charged electrodes, such as about 2,3, 4, 6, 8, 10, or more electrodes placed about the outer region of across-sectional area of the negative ion beam probe. Generally, moreelectrodes are required to converge or diverge a faster or higher energybeam.

In another embodiment, by reversing the polarity of electrodes in theabove example, the negative ion beam is made to diverge. Thus, thenegative ion beam path is optionally focused and expanded usingcombinations of electrode pairs. For example, if the electrode havingthe mesh across the negative ion beam path is made negative, then thenegative ion beam path is made to defocus. Hence, combinations ofelectrode pairs are used for focusing and defocusing a negative ion beampath, such as where a first pair includes a positively charged mesh forfocusing and a where a second pair includes a negatively charged meshfor defocusing.

Referring now to FIG. 7, the first partial vacuum system 330 is furtherdescribed. The first partial vacuum system 330 is an enclosed systemrunning from the hydrogen gas inlet port 312 to the tandem accelerator390 foil 395. The foil 395 is sealed directly or indirectly to the edgesof the vacuum tube 320 providing for a higher pressure, such as about10⁻⁵ torr, to be maintained on the first partial vacuum system 330 sideof the foil 395 and a lower pressure, such as about 10⁻⁷ torr, to bemaintained on the synchrotron side of the foil 390. By only pumpingfirst partial vacuum system 330 and by only semi-continuously operatingthe ion beam source vacuum based on sensor readings, the lifetime of thesemi-continuously operating pump is extended. The sensor readings arefurther described, infra.

Still referring to FIG. 7, the first partial vacuum system 330preferably includes: a first pump 332, such as a continuously operatingpump and/or a turbo molecular pump; a large holding volume 334; and asemi-continuously operating pump 336. Preferably, a pump controller 340receives a signal from a pressure sensor 342 monitoring pressure in thelarge holding volume 334. Upon a signal representative of a sufficientpressure in the large holding volume 334, the pump controller 340instructs an actuator 345 to open a valve 346 between the large holdingvolume and the semi-continuously operating pump 336 and the pumpcontroller 340 instructs the semi-continuously operating pump to turn onand pump to atmosphere residual gases out of the vacuum line 320 aboutthe charged particle stream. In this fashion, the lifetime of thesemi-continuously operating pump is extended by only operatingsemi-continuously and as needed. In one example, the semi-continuouslyoperating pump 336 operates for a few minutes every few hours, such as 5minutes every 4 hours, thereby extending a pump with a lifetime of about2,000 hours to about 96,000 hours.

Further, by isolating the inlet gas from the synchrotron vacuum system,the synchrotron vacuum pumps, such as turbo molecular pumps can operateover a longer lifetime as the synchrotron vacuum pumps have fewer gasmolecules to deal with. For example, the inlet gas is primarily hydrogengas but may contain impurities, such as nitrogen and carbon dioxide. Byisolating the inlet gases in the negative ion source system 310, firstpartial vacuum system 330, ion beam focusing system 350 and negative ionbeam side of the tandem accelerator 390, the synchrotron vacuum pumpscan operate at lower pressures with longer lifetimes, which increasesthe efficiency of the synchrotron 130.

Referring now to FIG. 8, another exemplary method of use of the chargedparticle beam system 100 is provided. The main controller 110, or one ormore sub-controllers, controls one or more of the subsystems toaccurately and precisely deliver protons to a tumor of a patient. Forexample, the main controller sends a message to the patient indicatingwhen or how to breath. The main controller 110 obtains a sensor readingfrom the patient interface module, such as a temperature breath sensoror a force reading indicative of where in a respiration cycle thesubject is. The main controller collects an image, such as a portion ofa body and/or of a tumor, from the imaging system 170. The maincontroller 110 also obtains position and/or timing information from thepatient interface module 150. The main controller 110 then optionallycontrols the injection system 120 to inject hydrogen gas into a negativeion beam source 310 and controls timing of extraction of the negativeion from the negative ion beam source 310. Optionally, the maincontroller controls ion beam focusing the ion beam focusing lens system350; acceleration of the proton beam with the tandem accelerator 390;and/or injection of the proton into the synchrotron 130. The synchrotrontypically contains at least an accelerator system 132 and an extractionsystem 134. The synchrotron preferably contains one or more of: turningmagnets, edge focusing magnets, magnetic field concentration magnets,winding and correction coils, and flat magnetic field incident surfaces,some of which contain elements under control by the main controller 110.The main controller preferably controls the proton beam within theaccelerator system, such as by controlling speed, trajectory, and/ortiming of the proton beam. The main controller then controls extractionof a proton beam from the accelerator through the extraction system 134.For example, the controller controls timing, energy, and/or intensity ofthe extracted beam. The controller 110 also preferably controlstargeting of the proton beam through the targeting/delivery system 140to the patient interface module 150. One or more components of thepatient interface module 150 are preferably controlled by the maincontroller 110, such as vertical position of the patient, rotationalposition of the patient, and patient chairpositioning/stabilization/control elements. Further, display elements ofthe display system 160 are preferably controlled via the main controller110. Displays, such as display screens, are typically provided to one ormore operators and/or to one or more patients. In one embodiment, themain controller 110 times the delivery of the proton beam from allsystems, such that protons are delivered in an optimal therapeuticmanner to the patient.

Circulating System

A synchrotron 130 preferably comprises a combination of straightsections 910 and ion beam turning sections 920. Hence, the circulatingpath of the protons is not circular in a synchrotron, but is rather apolygon with rounded corners.

In one illustrative embodiment, the synchrotron 130, which as alsoreferred to as an accelerator system, has four straight sections andfour turning sections. Examples of straight sections 910 include the:inflector 240, accelerator 270, extraction system 290, and deflector292. Along with the four straight sections are four ion beam turningsections 920, which are also referred to as magnet sections or turningsections. Turning sections are further described, infra.

Referring now to FIG. 9, an exemplary synchrotron is illustrated. Inthis example, protons delivered along the initial proton beam path 262are inflected into the circulating beam path with the inflector 240 andafter acceleration are extracted via a deflector 292 to a beam transportpath 268. In this example, the synchrotron 130 comprises four straightsections 910 and four bending or turning sections 920 where each of thefour turning sections use one or more magnets to turn the proton beamabout ninety degrees. As is further described, infra, the ability toclosely space the turning sections and efficiently turn the proton beamresults in shorter straight sections. Shorter straight sections allowsfor a synchrotron design without the use of focusing quadrupoles in thecirculating beam path of the synchrotron. The removal of the focusingquadrupoles from the circulating proton beam path results in a morecompact design. In this example, the illustrated synchrotron has about afive meter diameter versus eight meter and larger cross-sectionaldiameters for systems using a quadrupole focusing magnet in thecirculating proton beam path.

Referring now to FIG. 10, additional description of the first bending orturning section 920 is provided. Each of the turning sections preferablycomprises multiple magnets, such as about 2, 4, 6, 8, 10, or 12 magnets.In this example, four turning magnets 1010, 1020, 1030, 1040 in thefirst turning section 20 are used to illustrate key principles, whichare the same regardless of the number of magnets in a turning section920. A turning magnet 1010 is a particular type of main bending orcirculating magnet 250.

In physics, the Lorentz force is the force on a point charge due toelectromagnetic fields. The Lorentz force is given by equation 1 interms of magnetic fields with the election field terms not included.F=q(v×B)  eq. 1

In equation 1, F is the force in newtons; B is the magnetic field inTeslas; and v is the instantaneous velocity of the particles in metersper second.

Referring now to FIG. 11, an example of a single magnet bending orturning section 1010 is expanded. The turning section includes a gap1110 through which protons circulate. The gap 1110 is preferably a flatgap, allowing for a magnetic field across the gap 1110 that is moreuniform, even, and intense. A magnetic field enters the gap 1110 througha magnetic field incident surface and exits the gap 1110 through amagnetic field exiting surface. The gap 1110 runs in a vacuum tubebetween two magnet halves. The gap 1110 is controlled by at least twoparameters: (1) the gap 1110 is kept as large as possible to minimizeloss of protons and (2) the gap 1110 is kept as small as possible tominimize magnet sizes and the associated size and power requirements ofthe magnet power supplies. The flat nature of the gap 1110 allows for acompressed and more uniform magnetic field across the gap 1110. Oneexample of a gap dimension is to accommodate a vertical proton beam sizeof about two cm with a horizontal beam size of about five to six cm.

As described, supra, a larger gap size requires a larger power supply.For instance, if the gap 1110 size doubles in vertical size, then thepower supply requirements increase by about a factor of four. Theflatness of the gap 1110 is also important. For example, the flat natureof the gap 1110 allows for an increase in energy of the extractedprotons from about 250 to about 330 MeV. More particularly, if the gap1110 has an extremely flat surface, then the limits of a magnetic fieldof an iron magnet are reachable. An exemplary precision of the flatsurface of the gap 1110 is a polish of less than about five microns andpreferably with a polish of about one to three microns. Unevenness inthe surface results in imperfections in the applied magnetic field. Thepolished flat surface spreads unevenness of the applied magnetic field.

Still referring to FIG. 11, the charged particle beam moves through thegap 1110 with an instantaneous velocity, v. A first magnetic coil 1120and a second magnetic coil 1130 run above and below the gap 1110,respectively. Current running through the coils 1120, 1130 results in amagnetic field, B, running through the single magnet turning section1010. In this example, the magnetic field, B, runs upward, which resultsin a force, F, pushing the charged particle beam inward toward a centralpoint of the synchrotron, which turns the charged particle beam in anarc.

Still referring to FIG. 11, a portion of an optional second magnetbending or turning section 1020 is illustrated. The coils 1120, 1130typically have return elements 1140, 1150 or turns at the end of onemagnet, such as at the end of the first magnet turning section 1010. Theturns 1140, 1150 take space. The space reduces the percentage of thepath about one orbit of the synchrotron that is covered by the turningmagnets. This leads to portions of the circulating path where theprotons are not turned and/or focused and allows for portions of thecirculating path where the proton path defocuses. Thus, the spaceresults in a larger synchrotron. Therefore, the space between magnetturning sections 1160 is preferably minimized. The second turning magnetis used to illustrate that the coils 1120, 1130 optionally run along aplurality of magnets, such as 2, 3, 4, 5, 6, or more magnets. Coils1120, 1130 running across multiple turning section magnets allows fortwo turning section magnets to be spatially positioned closer to eachother due to the removal of the steric constraint of the turns, whichreduces and/or minimizes the space 1160 between two turning sectionmagnets.

Referring now to FIGS. 12 and 13, two illustrative 90 degree rotatedcross-sections of single magnet bending or turning sections 1010 arepresented. The magnet assembly has a first magnet 1210 and a secondmagnet 1220. A magnetic field induced by coils, described infra, runsbetween the first magnet 1210 to the second magnet 1220 across the gap1110. Return magnetic fields run through a first yoke 1212 and secondyoke 1222. The combined cross-section area of the return yokes roughlyapproximates the cross-sectional area of the first magnet 1210 or secondmagnet 1220. The charged particles run through the vacuum tube in thegap 1110. As illustrated, protons run into FIG. 12 through the gap 1110and the magnetic field, illustrated as vector B, applies a force F tothe protons pushing the protons towards the center of the synchrotron,which is off page to the right in FIG. 12. The magnetic field is createdusing windings. A first coil makes up a first winding coil 1250 and asecond coil of wire makes up a second winding coil 1260. Isolating orconcentrating gaps 1230, 1240, such as air gaps, isolate the iron basedyokes from the gap 1110. The gap 1110 is approximately flat to yield auniform magnetic field across the gap 1110, as described supra.

Still referring to FIG. 13, the ends of a single bending or turningmagnet are preferably beveled. Nearly perpendicular or right angle edgesof a turning magnet 1010 are represented by dashed lines 1374, 1384. Thedashed lines 1374, 1384 intersect at a point 1390 beyond the center ofthe synchrotron 280. Preferably, the edge of the turning magnet isbeveled at angles alpha, α, and beta, β, which are angles formed by afirst line 1372, 1382 going from an edge of the turning magnet 1010 andthe center 280 and a second line 1374, 1384 going from the same edge ofthe turning magnet and the intersecting point 1390. The angle alpha isused to describe the effect and the description of angle alpha appliesto angle beta, but angle alpha is optionally different from angle beta.The angle alpha provides an edge focusing effect. Beveling the edge ofthe turning magnet 1010 at angle alpha focuses the proton beam.

Multiple turning magnets provide multiple magnet edges that each haveedge focusing effects in the synchrotron 130. If only one turning magnetis used, then the beam is only focused once for angle alpha or twice forangle alpha and angle beta. However, by using smaller turning magnets,more turning magnets fit into the turning sections 920 of thesynchrotron 130. For example, if four magnets are used in a turningsection 920 of the synchrotron, then for a single turning section thereare eight possible edge focusing effect surfaces, two edges per magnet.The eight focusing surfaces yield a smaller cross-sectional beam size.This allows the use of a smaller gap 1110.

The use of multiple edge focusing effects in the turning magnets resultsin not only a smaller gap 1110, but also the use of smaller magnets andsmaller power supplies. For a synchrotron 130 having four turningsections 920 where each turning sections has four turning magnets andeach turning magnet has two focusing edges, a total of thirty-twofocusing edges exist for each orbit of the protons in the circulatingpath of the synchrotron 130. Similarly, if 2, 6, or 8 magnets are usedin a given turning section, or if 2, 3, 5, or 6 turning sections areused, then the number of edge focusing surfaces expands or contractsaccording to equation 2.

$\begin{matrix}{{TFE} = {{NTS}*\frac{M}{NTS}*\frac{FE}{M}}} & {{eq}.\mspace{14mu} 2}\end{matrix}$where TFE is the number of total focusing edges, NTS is the number ofturning sections, M is the number of magnets, and FE is the number offocusing edges. Naturally, not all magnets are necessarily beveled andsome magnets are optionally beveled on only one edge.

The inventors have determined that multiple smaller magnets havebenefits over fewer larger magnets. For example, the use of 16 smallmagnets yields 32 focusing edges whereas the use of 4 larger magnetsyields only 8 focusing edges. The use of a synchrotron having morefocusing edges results in a circulating path of the synchrotron builtwithout the use of focusing quadrupoles magnets. All prior artsynchrotrons use quadrupoles in the circulating path of the synchrotron.Further, the use of quadrupoles in the circulating path necessitatesadditional straight sections in the circulating path of the synchrotron.Thus, the use of quadrupoles in the circulating path of a synchrotronresults in synchrotrons having larger diameters, circulating beampathlengths, and/or larger circumferences.

In various embodiments of the system described herein, the synchrotronhas any combination of:

-   -   at least 4 and preferably 6, 8, 10, or more edge focusing edges        per 90 degrees of turn of the charged particle beam in a        synchrotron having four turning sections;    -   at least about 16 and preferably about 24, 32, or more edge        focusing edges per orbit of the charged particle beam in the        synchrotron;    -   only 4 turning sections where each of the turning sections        includes at least 4 and preferably 8 edge focusing edges;    -   an equal number of straight sections and turning sections;    -   exactly 4 turning sections;    -   at least 4 edge focusing edges per turning section;    -   no quadrupoles in the circulating path of the synchrotron;    -   a rounded corner rectangular polygon configuration;    -   a circumference of less than 60 meters;    -   a circumference of less than 60 meters and 32 edge focusing        surfaces; and/or    -   any of about 8, 16, 24, or 32 non-quadrupole magnets per        circulating path of the synchrotron, where the non-quadrupole        magnets include edge focusing edges.

Referring now to FIG. 12, the incident magnetic field surface 1270 ofthe first magnet 1210 is further described. FIG. 12 is not to scale andis illustrative in nature. Local imperfections or unevenness in qualityof the finish of the incident surface 1270 results in inhomogeneities orimperfections in the magnetic field applied to the gap 1110. Preferably,the incident surface 1270 is flat, such as to within about a zero tothree micron finish polish, or less preferably to about a ten micronfinish polish.

Referring now to FIG. 14, additional optional magnet elements, of themagnet cross-section illustratively represented in FIG. 12, aredescribed. The first magnet 1210 preferably contains an initialcross-sectional distance 1410 of the iron based core. The contours ofthe magnetic field are shaped by the magnets 1210, 1220 and the yokes1212, 1222. The iron based core tapers to a second cross-sectionaldistance 1420. The magnetic field in the magnet preferentially stays inthe iron based core as opposed to the gaps 1230, 1240. As thecross-sectional distance decreases from the initial cross-sectionaldistance 1410 to the final cross-sectional distance 1420, the magneticfield concentrates. The change in shape of the magnet from the longerdistance 1410 to the smaller distance 1420 acts as an amplifier. Theconcentration of the magnetic field is illustrated by representing aninitial density of magnetic field vectors 1430 in the initialcross-section 1410 to a concentrated density of magnetic field vectors1440 in the final cross-section 1420. The concentration of the magneticfield due to the geometry of the turning magnets results in fewerwinding coils 1250, 1260 being required and also a smaller power supplyto the coils being required.

Example I

In one example, the initial cross-section distance 1410 is about fifteencentimeters and the final cross-section distance 1420 is about tencentimeters. Using the provided numbers, the concentration of themagnetic field is about 15/10 or 1.5 times at the incident surface 1270of the gap 1110, though the relationship is not linear. The taper 1460has a slope, such as about 20, 40, or 60 degrees. The concentration ofthe magnetic field, such as by 1.5 times, leads to a correspondingdecrease in power consumption requirements to the magnets.

Referring now to FIG. 15, an additional example of geometry of themagnet used to concentrate the magnetic field is illustrated. Asillustrated in FIG. 14, the first magnet 1210 preferably contains aninitial cross-sectional distance 1410 of the iron based core. Thecontours of the magnetic field are shaped by the magnets 1210, 1220 andthe yokes 1212, 1222. In this example, the core tapers to a secondcross-sectional distance 1420 with a smaller angle theta, θ. Asdescribed, supra, the magnetic field in the magnet preferentially staysin the iron based core as opposed to the gaps 1230, 1240. As thecross-sectional distance decreases from the initial cross-sectionaldistance 1410 to the final cross-sectional distance 1420, the magneticfield concentrates. The smaller angle, theta, results in a greateramplification of the magnetic field in going from the longer distance1410 to the smaller distance 1420. The concentration of the magneticfield is illustrated by representing an initial density of magneticfield vectors 1430 in the initial cross-section 1410 to a concentrateddensity of magnetic field vectors 1440 in the final cross-section 1420.The concentration of the magnetic field due to the geometry of theturning magnets results in fewer winding coils 1250, 1260 being requiredand also a smaller power supply to the winding coils 1250, 1260 beingrequired.

Still referring to FIG. 15, optional correction coils 1510, 1520 areillustrated that are used to correct the strength of one or more turningmagnets. The correction coils 1520, 1530 supplement the winding coils1250, 1260. The correction coils 1510, 1520 have correction coil powersupplies that are separate from winding coil power supplies used withthe winding coils 1250, 1260. The correction coil power suppliestypically operate at a fraction of the power required compared to thewinding coil power supplies, such as about 1, 2, 3, 5, 7, or 10 percentof the power and more preferably about 1 or 2 percent of the power usedwith the winding coils 1250, 1260. The smaller operating power appliedto the correction coils 1510, 1520 allows for more accurate and/orprecise control of the correction coils. The correction coils are usedto adjust for imperfection in the turning magnets. Optionally, separatecorrection coils are used for each turning magnet allowing individualtuning of the magnetic field for each turning magnet, which easesquality requirements in the manufacture of each turning magnet.

Referring now to FIG. 16, an example of winding coils and correctioncoils about a plurality of turning magnets in an ion beam turningsection 920 is illustrated. One or more high precision magnetic fieldsensors are placed into the synchrotron and are used to measure themagnetic field at or near the proton beam path. For example, themagnetic sensors are optionally placed between turning magnets and/orwithin a turning magnet, such as at or near the gap 1110 or at or nearthe magnet core or yoke. The sensors are part of a feedback system tothe correction coils. Thus, the system preferably stabilizes themagnetic field in the synchrotron rather than stabilizing the currentapplied to the magnets. Stabilization of the magnetic field allows thesynchrotron to come to a new energy level quickly. This allows thesystem to be controlled to an operator or algorithm selected energylevel with each pulse of the synchrotron and/or with each breath of thepatient.

The winding and/or correction coils correct 1, 2, 3, or 4 turningmagnets, and preferably correct a magnetic field generated by twoturning magnets. A winding or correction coil covering multiple magnetsreduces space between magnets as fewer winding or correction coil endsare required, which occupy space. In the illustrated example, acorrection coil 1610 winds around a single turning magnet. In anotherexample, a correction coil 1620 wraps around two magnets and corrects awinding coil 1630 wrapping around the two magnets.

Example II

Referring now to FIG. 17, an example is used to clarify the magneticfield control using a feedback loop 1700 to change delivery times and/orperiods of proton pulse delivery. In one case, a respiratory sensor 1710senses the respiration cycle of the subject. The respiratory sensorsends the information to an algorithm in a magnetic field controller1720, typically via the patient interface module 150 and/or via the maincontroller 110 or a subcomponent thereof. The algorithm predicts and/ormeasures when the subject is at a particular point in the respirationcycle, such as at the bottom of a breath. Magnetic field sensors 1730are used as input to the magnetic field controller, which controls amagnet power supply 1740 for a given magnetic field 1750, such as withina first turning magnet 1010 of a synchrotron 130. The control feedbackloop is thus used to dial the synchrotron to a selected energy level anddeliver protons with the desired energy at a selected point in time,such as at the bottom of the breath. More particularly, the maincontroller injects protons into the synchrotron and accelerates theprotons in a manner that combined with extraction delivers the protonsto the tumor at a selected point in the breathing cycle. Intensity ofthe proton beam is also selectable and controllable by the maincontroller at this stage. The feedback control to the correction coilsallows rapid selection of energy levels of the synchrotron that are tiedto the patient's respiration cycle. This system is in stark contrast toa system where the current is stabilized and the synchrotron deliverpulses with a period, such as 10 or 20 cycles per second with a fixedperiod.

The feedback or the magnetic field design coupled with the correctioncoils allows for the extraction cycle to match the varying respiratoryrate of the patient.

Traditional extraction systems do not allow this control as magnets havememories in terms of both magnitude and amplitude of a sine wave. Hence,in a traditional system, in order to change frequency, slow changes incurrent must be used. However, with the use of the feedback loop usingthe magnetic field sensors, the frequency and energy level of thesynchrotron are rapidly adjustable. Further aiding this process is theuse of a novel extraction system that allows for acceleration of theprotons during the extraction process, described infra.

Example III

Referring again to FIG. 16, an example of a winding coil 1630 thatcovers two turning magnets 1010, 1020 is provided. Optionally, a firstwinding coil 1640 covers two magnets and a second winding coil coversanother two magnets. As described, supra, this system reduces spacebetween turning section allowing more magnetic field to be applied perradian of turn. A first correction coil 1610 is illustrated that is usedto correct the magnetic field for the first turning magnet 1010. Asecond correction coil 1620 is illustrated that is used to correct themagnetic field for a winding coil 1630 about two turning magnets.Individual correction coils for each turning magnet are preferred andindividual correction coils yield the most precise and/or accuratemagnetic field in each turning section. Particularly, the individualcorrection coil 1610 is used to compensate for imperfections in theindividual magnet of a given turning section. Hence, with a series ofmagnetic field sensors, corresponding magnetic fields are individuallyadjustable in a series of feedback loops, via a magnetic fieldmonitoring system, as an independent coil is used for each turningsection. Alternatively, a multiple magnet correction coil is used tocorrect the magnetic field for a plurality of turning section magnets.

Flat Gap Surface

While the gap surface is described in terms of the first turning magnet1010, the discussion applies to each of the turning magnets in thesynchrotron. Similarly, while the gap 1110 surface is described in termsof the magnetic field incident surface 1270, the discussion additionallyoptionally applies to the magnetic field exiting surface 1280.

The magnetic field incident surface 1270 of the first magnet 1210 ispreferably about flat, such as to within about a zero to three micronfinish polish or less preferably to about a ten micron finish polish. Bybeing very flat, the polished surface spreads the unevenness of theapplied magnetic field across the gap 1110. The very flat surface, suchas about 0, 1, 2, 4, 6, 8, 10, 15, or 20 micron finish, allows for asmaller gap size, a smaller applied magnetic field, smaller powersupplies, and tighter control of the proton beam cross-sectional area.

Proton Beam Extraction

Referring now to FIG. 18, an exemplary proton extraction process fromthe synchrotron 130 is illustrated. For clarity, FIG. 18 removeselements represented in FIG. 2, such as the turning magnets, whichallows for greater clarity of presentation of the proton beam path as afunction of time. Generally, protons are extracted from the synchrotron130 by slowing the protons. As described, supra, the protons wereinitially accelerated in a circulating path 264, which is maintainedwith a plurality of main bending magnets 250. The circulating path isreferred to herein as an original central beamline 264. The protonsrepeatedly cycle around a central point in the synchrotron 280. Theproton path traverses through a radio frequency (RF) cavity system 1810.To initiate extraction, an RF field is applied across a first blade 1812and a second blade 1814, in the RF cavity system 1810. The first blade1812 and second blade 1814 are referred to herein as a first pair ofblades.

In the proton extraction process, an RF voltage is applied across thefirst pair of blades, where the first blade 1812 of the first pair ofblades is on one side of the circulating proton beam path 264 and thesecond blade 1814 of the first pair of blades is on an opposite side ofthe circulating proton beam path 264. The applied RF field appliesenergy to the circulating charged-particle beam. The applied RF fieldalters the orbiting or circulating beam path slightly of the protonsfrom the original central beamline 264 to an altered circulating beampath 265. Upon a second pass of the protons through the RF cavitysystem, the RF field further moves the protons off of the originalproton beamline 264. For example, if the original beamline is consideredas a circular path, then the altered beamline is slightly elliptical.The applied RF field is timed to apply outward or inward movement to agiven band of protons circulating in the synchrotron accelerator. Eachorbit of the protons is slightly more off axis compared to the originalcirculating beam path 264. Successive passes of the protons through theRF cavity system are forced further and further from the originalcentral beamline 264 by altering the direction and/or intensity of theRF field with each successive pass of the proton beam through the RFfield.

The RF voltage is frequency modulated at a frequency about equal to theperiod of one proton cycling around the synchrotron for one revolutionor at a frequency than is an integral multiplier of the period of oneproton cycling about the synchrotron. The applied RF frequency modulatedvoltage excites a betatron oscillation. For example, the oscillation isa sine wave motion of the protons. The process of timing the RF field toa given proton beam within the RF cavity system is repeated thousands oftimes with each successive pass of the protons being moved approximatelyone micrometer further off of the original central beamline 264. Forclarity, the approximately 1000 changing beam paths with each successivepath of a given band of protons through the RF field are illustrated asthe altered beam path 265.

With a sufficient sine wave betatron amplitude, the altered circulatingbeam path 265 touches or traverses a material 1830, such as a foil or asheet of foil. The foil is preferably a lightweight material, such asberyllium, a lithium hydride, a carbon sheet, or a material of lownuclear charge. A material of low nuclear charge is a material composedof atoms consisting essentially of atoms having six or fewer protons.The foil is preferably about 10 to 150 microns thick, is more preferably30 to 100 microns thick, and is still more preferably about 40 to 60microns thick. In one example, the foil is beryllium with a thickness ofabout 50 microns. When the protons traverse through the foil, energy ofthe protons is lost and the speed of the protons is reduced. Typically,a current is also generated, described infra. Protons moving at a slowerspeed travel in the synchrotron with a reduced radius of curvature 266compared to either the original central beamline 264 or the alteredcirculating path 265. The reduced radius of curvature 266 path is alsoreferred to herein as a path having a smaller diameter of trajectory ora path having protons with reduced energy. The reduced radius ofcurvature 266 is typically about two millimeters less than a radius ofcurvature of the last pass of the protons along the altered proton beampath 265.

The thickness of the material 1830 is optionally adjusted to created achange in the radius of curvature, such as about ½, 1, 2, 3, or 4 mmless than the last pass of the protons 265 or original radius ofcurvature 264. Protons moving with the smaller radius of curvaturetravel between a second pair of blades. In one case, the second pair ofblades is physically distinct and/or are separated from the first pairof blades. In a second case, one of the first pair of blades is also amember of the second pair of blades. For example, the second pair ofblades is the second blade 1814 and a third blade 1816 in the RF cavitysystem 1810. A high voltage DC signal, such as about 1 to 5 kV, is thenapplied across the second pair of blades, which directs the protons outof the synchrotron through an extraction magnet 292, such as a Lambersonextraction magnet, into a transport path 268.

Control of acceleration of the charged particle beam path in thesynchrotron with the accelerator and/or applied fields of the turningmagnets in combination with the above described extraction system allowsfor control of the intensity of the extracted proton beam, whereintensity is a proton flux per unit time or the number of protonsextracted as a function of time. For example, when a current is measuredbeyond a threshold, the RF field modulation in the RF cavity system isterminated or reinitiated to establish a subsequent cycle of proton beamextraction. This process is repeated to yield many cycles of proton beamextraction from the synchrotron accelerator.

Because the extraction system does not depend on change in magneticfield properties, it allows the synchrotron to continue to operate inacceleration or deceleration mode during the extraction process. Stateddifferently, the extraction process does not interfere with synchrotronacceleration. In stark contrast, traditional extraction systemsintroduce a new magnetic field, such as via a hexapole, during theextraction process. More particularly, traditional synchrotrons have amagnet, such as a hexapole magnet, that is off during an accelerationstage. During the extraction phase, the hexapole magnetic field isintroduced to the circulating path of the synchrotron. The introductionof the magnetic field necessitates two distinct modes, an accelerationmode and an extraction mode, which are mutually exclusive in time.

Charged Particle Beam Intensity Control

Control of applied field, such as a radio-frequency (RF) field,frequency and magnitude in the RF cavity system 1810 allows forintensity control of the extracted proton beam, where intensity isextracted proton flux per unit time or the number of protons extractedas a function of time.

Referring still to FIG. 18, when protons in the proton beam hit thematerial 1830 electrons are given off resulting in a current. Theresulting current is converted to a voltage and is used as part of a ionbeam intensity monitoring system or as part of an ion beam feedback loopfor controlling beam intensity. The voltage is optionally measured andsent to the main controller 110 or to a controller subsystem 1840. Moreparticularly, when protons in the charged particle beam path passthrough the material 1830, some of the protons lose a small fraction oftheir energy, such as about one-tenth of a percent, which results in asecondary electron. That is, protons in the charged particle beam pushsome electrons when passing through material 1830 giving the electronsenough energy to cause secondary emission. The resulting electron flowresults in a current or signal that is proportional to the number ofprotons going through the target material 1830. The resulting current ispreferably converted to voltage and amplified. The resulting signal isreferred to as a measured intensity signal.

The amplified signal or measured intensity signal resulting from theprotons passing through the material 1830 is preferably used incontrolling the intensity of the extracted protons. For example, themeasured intensity signal is compared to a goal signal, which ispredetermined in an irradiation of the tumor plan. The differencebetween the measured intensity signal and the planned for goal signal iscalculated. The difference is used as a control to the RF generator.Hence, the measured flow of current resulting from the protons passingthrough the material 1830 is used as a control in the RF generator toincrease or decrease the number of protons undergoing betatronoscillation and striking the material 1830. Hence, the voltagedetermined off of the material 1830 is used as a measure of the orbitalpath and is used as a feedback control to control the RF cavity system.Alternatively, the measured intensity signal is not used in the feedbackcontrol and is just used as a monitor of the intensity of the extractedprotons.

As described, supra, the photons striking the material 1830 is a step inthe extraction of the protons from the synchrotron 130. Hence, themeasured intensity signal is used to change the number of protons perunit time being extracted, which is referred to as intensity of theproton beam. The intensity of the proton beam is thus under algorithmcontrol. Further, the intensity of the proton beam is controlledseparately from the velocity of the protons in the synchrotron 130.Hence, intensity of the protons extracted and the energy of the protonsextracted are independently variable.

For example, protons initially move at an equilibrium trajectory in thesynchrotron 130. An RF field is used to excite the protons into abetatron oscillation. In one case, the frequency of the protons orbit isabout 10 MHz. In one example, in about one millisecond or after about10,000 orbits, the first protons hit an outer edge of the targetmaterial 130. The specific frequency is dependent upon the period of theorbit. Upon hitting the material 130, the protons push electrons throughthe foil to produce a current. The current is converted to voltage andamplified to yield a measured intensity signal. The measured intensitysignal is used as a feedback input to control the applied RF magnitude,RF frequency, or RF field. Preferably, the measured intensity signal iscompared to a target signal and a measure of the difference between themeasured intensity signal and target signal is used to adjust theapplied RF field in the RF cavity system 1810 in the extraction systemto control the intensity of the protons in the extraction step. Statedagain, the signal resulting from the protons striking and/or passingthrough the material 130 is used as an input in RF field modulation. Anincrease in the magnitude of the RF modulation results in protonshitting the foil or material 130 sooner. By increasing the RF, moreprotons are pushed into the foil, which results in an increasedintensity, or more protons per unit time, of protons extracted from thesynchrotron 130.

In another example, a detector 1850 external to the synchrotron 130 isused to determine the flux of protons extracted from the synchrotron anda signal from the external detector is used to alter the RF field or RFmodulation in the RF cavity system 1810. Here the external detectorgenerates an external signal, which is used in a manner similar to themeasured intensity signal, described in the preceding paragraphs.

In yet another example, when a current from material 130 resulting fromprotons passing through or hitting material is measured beyond athreshold, the RF field modulation in the RF cavity system is terminatedor reinitiated to establish a subsequent cycle of proton beamextraction. This process is repeated to yield many cycles of proton beamextraction from the synchrotron accelerator.

In still yet another embodiment, intensity modulation of the extractedproton beam is controlled by the main controller 110. The maincontroller 110 optionally and/or additionally controls timing ofextraction of the charged particle beam and energy of the extractedproton beam.

The benefits of the system include a multi-dimensional scanning system.Particularly, the system allows independence in: (1) energy of theprotons extracted and (2) intensity of the protons extracted. That is,energy of the protons extracted is controlled by an energy controlsystem and an intensity control system controls the intensity of theextracted protons. The energy control system and intensity controlsystem are optionally independently controlled. Preferably, the maincontroller 110 controls the energy control system and the maincontroller simultaneously controls the intensity control system to yieldan extracted proton beam with controlled energy and controlled intensitywhere the controlled energy and controlled intensity are independentlyvariable. Thus the irradiation spot hitting the tumor is underindependent control of:

-   -   time;    -   energy;    -   intensity;    -   x-axis position, where the x-axis represents horizontal movement        of the proton beam relative to the patient, and    -   y-axis position, where the y-axis represents vertical movement        of the proton beam relative to the patient.

In addition, the patient is optionally independently rotated relative toa translational axis of the proton beam at the same time.

Patient Positioning

Referring now to FIG. 19, the patient is preferably positioned on orwithin a patient positioning system 1910 of the patient interface module150. The patient positioning system 1910 is used to translate thepatient and/or rotate the patient into a zone where the proton beam canscan the tumor using a scanning system 140 or proton targeting system,described infra. Essentially, the patient positioning system 1910performs large movements of the patient to place the tumor near thecenter of a proton beam path 268 and the proton scanning or targetingsystem 140 performs fine movements of the momentary beam position 269 intargeting the tumor 1920. To illustrate, FIG. 19 shows the momentaryproton beam position 269 and a range of scannable positions 1940 usingthe proton scanning or targeting system 140, where the scannablepositions 1940 are about the tumor 1920 of the patient 1930. Thisillustratively shows that the y-axis movement of the patient occurs on ascale of the body, such as adjustment of about 1, 2, 3, or 4 feet, whilethe scannable region of the proton beam 268 covers a portion of thebody, such as a region of about 1, 2, 4, 6, 8, 10, or 12 inches. Thepatient positioning system and its rotation and/or translation of thepatient combines with the proton targeting system to yield preciseand/or accurate delivery of the protons to the tumor.

Referring still to FIG. 19, the patient positioning system 1910optionally includes a bottom unit 1912 and a top unit 1914, such asdiscs or a platform. Referring now to FIG. 19A, the patient positioningunit 1910 is preferably y-axis adjustable 1916 to allow verticalshifting of the patient relative to the proton therapy beam 268.Preferably, the vertical motion of the patient positioning unit 1910 isabout 10, 20, 30, or 50 centimeters per minute. Referring now to FIG.19B, the patient positioning unit 1910 is also preferably rotatable 1917about a rotation axis, such as about the y-axis, to allow rotationalcontrol and positioning of the patient relative to the proton beam path268. Preferably the rotational motion of the patient positioning unit1910 is about 360 degrees per minute. Optionally, the patientpositioning unit rotates about 45, 90, or 180 degrees. Optionally, thepatient positioning unit 1910 rotates at a rate of about 45, 90, 180,360, 720, or 1080 degrees per minute. The rotation of the positioningunit 1917 is illustrated about the rotation axis at two distinct times,t₁ and t₂. Protons are optionally delivered to the tumor 1920 at n timeswhere each of the n times represent different directions of the incidentproton beam 269 hitting the patient 1930 due to rotation of the patient1917 about the rotation axis.

Any of the semi-vertical, sitting, or laying patient positioningembodiments described, infra, are optionally vertically translatablealong the y-axis or rotatable about the rotation or y-axis.

Preferably, the top and bottom units 1912, 1914 move together, such thatthey rotate at the same rates and translate in position at the samerates. Optionally, the top and bottom units 1912, 1914 are independentlyadjustable along the y-axis to allow a difference in distance betweenthe top and bottom units 1912, 1914. Motors, power supplies, andmechanical assemblies for moving the top and bottom units 1912, 1914 arepreferably located out of the proton beam path 269, such as below thebottom unit 1912 and/or above the top unit 1914. This is preferable asthe patient positioning unit 1910 is preferably rotatable about 360degrees and the motors, power supplies, and mechanical assembliesinterfere with the protons if positioned in the proton beam path 269

Proton Beam Position Control

Referring now to FIG. 20, a beam delivery and tissue volume scanningsystem is illustrated. Presently, the worldwide radiotherapy communityuses a method of dose field forming using a pencil beam scanning system.In stark contrast, FIG. 20 illustrates a spot scanning system or tissuevolume scanning system. In the tissue volume scanning system, the protonbeam is controlled, in terms of transportation and distribution, usingan inexpensive and precise scanning system. The scanning system is anactive system, where the beam is focused into a spot focal point ofabout one-half, one, two, or three millimeters in diameter. The focalpoint is translated along two axes while simultaneously altering theapplied energy of the proton beam, which effectively changes the thirddimension of the focal point. The system is applicable in combinationwith the above described rotation of the body, which preferably occursin-between individual moments or cycles of proton delivery to the tumor.Optionally, the rotation of the body by the above described systemoccurs continuously and simultaneously with proton delivery to thetumor.

For example, in the illustrated system in FIG. 20A, the spot istranslated horizontally, is moved down a vertical, and is then backalong the horizontal axis. In this example, current is used to control avertical scanning system having at least one magnet. The applied currentalters the magnetic field of the vertical scanning system to control thevertical deflection of the proton beam. Similarly, a horizontal scanningmagnet system controls the horizontal deflection of the proton beam. Thedegree of transport along each axes is controlled to conform to thetumor cross-section at the given depth. The depth is controlled bychanging the energy of the proton beam. For example, the proton beamenergy is decreased, so as to define a new penetration depth, and thescanning process is repeated along the horizontal and vertical axescovering a new cross-sectional area of the tumor. Combined, the threeaxes of control allow scanning or movement of the proton beam focalpoint over the entire volume of the cancerous tumor. The time at eachspot and the direction into the body for each spot is controlled toyield the desired radiation does at each sub-volume of the cancerousvolume while distributing energy hitting outside of the tumor.

The focused beam spot volume dimension is preferably tightly controlledto a diameter of about 0.5, 1, or 2 millimeters, but is alternativelyseveral centimeters in diameter. Preferred design controls allowscanning in two directions with: (1) a vertical amplitude of about 100mm amplitude and frequency up to 200 Hz; and (2) a horizontal amplitudeof about 700 mm amplitude and frequency up to 1 Hz. More or lessamplitude in each axis is possible by altering the scanning magnetsystems.

In FIG. 20A, the proton beam is illustrated along a z-axis controlled bythe beam energy, the horizontal movement is along an x-axis, and thevertical direction is along a y-axis. The distance the protons movealong the z-axis into the tissue, in this example, is controlled by thekinetic energy of the proton. This coordinate system is arbitrary andexemplary. The actual control of the proton beam is controlled in3-dimensional space using two scanning magnet systems and by controllingthe kinetic energy of the proton beam. The use of the extraction system,described supra, allows for different scanning patterns. Particularly,the system allows simultaneous adjustment of the x-, y-, and z-axes inthe irradiation of the solid tumor. Stated again, instead of scanningalong an x,y-plane and then adjusting energy of the protons, such aswith a range modulation wheel, the system allows for moving along thez-axes while simultaneously adjusting the x- and or y-axes. Hence,rather than irradiating slices of the tumor, the tumor is optionallyirradiated in three simultaneous dimensions. For example, the tumor isirradiated around an outer edge of the tumor in three dimensions. Thenthe tumor is irradiated around an outer edge of an internal section ofthe tumor. This process is repeated until the entire tumor isirradiated. The outer edge irradiation is preferably coupled withsimultaneous rotation of the subject, such as about a vertical y-axis.This system allows for maximum efficiency of deposition of protons tothe tumor, as defined using the Bragg peak, to the tumor itself withminimal delivery of proton energy to surrounding healthy tissue.

Combined, the system allows for multi-axes control of the chargedparticle beam system in a small space with small power supply. Forexample, the system uses multiple magnets where each magnet has at leastone edge focusing effect in each turning section of the synchrotronand/or multiple magnets having concentrating magnetic field geometry, asdescribed supra. The multiple edge focusing effects in the circulatingbeam path of the synchrotron combined with the concentration geometry ofthe magnets and described extraction system yields a synchrotron having:

-   -   a small circumference system, such as less than about 50 meters;    -   a vertical proton beam size gap of about 2 cm;    -   corresponding reduced power supply requirements associated with        the reduced gap size;    -   an extraction system not requiring a newly introduced magnetic        field;    -   acceleration or deceleration of the protons during extraction;        and    -   control of z-axis energy during extraction.

The result is a 3-dimensional scanning system, x-, y-, and z-axescontrol, where the z-axes control resides in the synchrotron and wherethe z-axes energy is variably controlled during the extraction processinside the synchrotron.

Referring now to FIG. 20B, an example of a proton scanning or targetingsystem 140 used to direct the protons to the tumor with 4-dimensionalscanning control is provided, where the 4-dimensional scanning controlis along the x-, y-, and z-axes along with intensity control, asdescribed supra. A fifth axis is time. Typically, charged particlestraveling along the transport path 268 are directed through a first axiscontrol element 142, such as a vertical control, and a second axiscontrol element 144, such as a horizontal control and into a tumor 1920.As described, supra, the extraction system also allows for simultaneousvariation in the z-axis. Further, as describe, supra, the intensity ordose of the extracted beam is optionally simultaneously andindependently controlled and varied. Thus instead of irradiating a sliceof the tumor, as in FIG. 20A, all four dimensions defining the targetingspot of the proton delivery in the tumor are simultaneously variable.The simultaneous variation of the proton delivery spot is illustrated inFIG. 20B by the spot delivery path 269. In the illustrated case, theprotons are initially directed around an outer edge of the tumor and arethen directed around an inner radius of the tumor. Combined withrotation of the subject about a vertical axis, a multi-fieldillumination process is used where a not yet irradiated portion of thetumor is preferably irradiated at the further distance of the tumor fromthe proton entry point into the body. This yields the greatestpercentage of the proton delivery, as defined by the Bragg peak, intothe tumor and minimizes damage to peripheral healthy tissue.

Imaging/X-Ray System

Herein, an X-ray system is used to illustrate an imaging system.

Timing

An X-ray is preferably collected either (1) just before or (2)concurrently with treating a subject with proton therapy for a couple ofreasons.

First, movement of the body, described supra, changes the local positionof the tumor in the body relative to other body constituents. If thesubject has an X-ray taken and is then bodily moved to a protontreatment room, accurate alignment of the proton beam to the tumor isproblematic. Alignment of the proton beam to the tumor using one or moreX-rays is best performed at the time of proton delivery or in theseconds or minutes immediately prior to proton delivery and after thepatient is placed into a therapeutic body position, which is typically afixed position or partially immobilized position.

Second, the X-ray taken after positioning the patient is used forverification of proton beam alignment to a targeted position, such as atumor and/or internal organ position.

Positioning

An X-ray is preferably taken just before treating the subject to aid inpatient positioning. For positioning purposes, an X-ray of a large bodyarea is not needed. In one embodiment, an X-ray of only a local area iscollected. When collecting an X-ray, the X-ray has an X-ray path. Theproton beam has a proton beam path. Overlaying the X-ray path with theproton beam path is one method of aligning the proton beam to the tumor.However, this method involves putting the X-ray equipment into theproton beam path, taking the X-ray, and then moving the X-ray equipmentout of the beam path. This process takes time. The elapsed time whilethe X-ray equipment moves has a couple of detrimental effects. First,during the time required to move the X-ray equipment, the body moves.The resulting movement decreases precision and/or accuracy of subsequentproton beam alignment to the tumor. Second, the time required to movethe X-ray equipment is time that the proton beam therapy system is notin use, which decreases the total efficiency of the proton beam therapysystem.

X-Ray Source Lifetime

It is desirable to have components in the particle beam therapy systemthat require minimal or no maintenance over the lifetime of the particlebeam therapy system. For example, it is desirable to equip the protonbeam therapy system with an X-ray system having a long lifetime source,such as a lifetime of about 20 years.

In one system, described infra, electrons are used to create X-rays. Theelectrons are generated at a cathode where the lifetime of the cathodeis temperature dependent. Analogous to a light bulb, where the filamentis kept in equilibrium, the cathode temperature is held in equilibriumat temperatures at about 200, 500, or 1000 degrees Celsius. Reduction ofthe cathode temperature results in increased lifetime of the cathode.Hence, the cathode used in generating the electrons is preferably heldat as low of a temperature as possible. However, if the temperature ofthe cathode is reduced, then electron emissions also decrease. Toovercome the need for more electrons at lower temperatures, a largecathode is used and the generated electrons are concentrated. Theprocess is analogous to compressing electrons in an electron gun;however, here the compression techniques are adapted to apply toenhancing an X-ray tube lifetime.

Referring now to FIG. 21, an example of an X-ray generation device 2100having an enhanced lifetime is provided. Electrons 2120 are generated ata cathode 2110, focused with a control electrode 2112, and acceleratedwith a series of accelerating electrodes 2140. The accelerated electrons2150 impact an X-ray generation source 2148 resulting in generatedX-rays that are then directed along an X-ray path 2270 to the subject1930. The concentrating of the electrons from a first diameter 2115 to asecond diameter 2116 allows the cathode to operate at a reducedtemperature and still yield the necessary amplified level of electronsat the X-ray generation source 2148. In one example, the X-raygeneration source is the anode coupled with the cathode 2110 and/or theX-ray generation source is substantially composed of tungsten.

Still referring to FIG. 21, a more detailed description of an exemplaryX-ray generation device 2100 is described. An anode 2114/cathode 2110pair is used to generated electrons. The electrons 2120 are generated atthe cathode 2110 having a first diameter 2115, which is denoted d₁. Thecontrol electrodes 2112 attract the generated electrons 2120. Forexample, if the cathode is held at about −150 kV and the controlelectrode is held at about −149 kV, then the generated electrons 2120are attracted toward the control electrodes 2112 and focused. A seriesof accelerating electrodes 2140 are then used to accelerate theelectrons into a substantially parallel path 2150 with a smallerdiameter 2116, which is denoted d₂. For example, with the cathode heldat −150 kV, a first, second, third, and fourth accelerating electrodes2142, 2144, 2146, 2148 are held at about −120, −90, −60, and −30 kV,respectively. If a thinner body part is to be analyzed, then the cathode2110 is held at a smaller level, such as about −90 kV and the controlelectrode, first, second, third, and fourth electrode are each adjustedto lower levels. Generally, the voltage difference from the cathode tofourth electrode is less for a smaller negative voltage at the cathodeand vise-versa. The accelerated electrons 2150 are optionally passedthrough a magnetic lens 2160 for adjustment of beam size, such as acylindrical magnetic lens. The electrons are also optionally focusedusing quadrupole magnets 2170, which focus in one direction and defocusin another direction. The accelerated electrons 2150, which are nowadjusted in beam size and focused strike an X-ray generation source2148, such as tungsten, resulting in generated X-rays that pass throughan optional blocker 2262 and proceed along an X-ray path 2170 to thesubject. The X-ray generation source 2148 is optionally cooled with acooling element 2149, such as water touching or thermally connected to abackside of the X-ray generation source 2148. The concentrating of theelectrons from a first diameter 2115 to a second diameter 2116 allowsthe cathode to operate at a reduced temperature and still yield thenecessary amplified level of electrons at the X-ray generation source2148.

More generally, the X-ray generation device 2100 produces electronshaving initial vectors. One or more of the control electrode 2112,accelerating electrodes 2140, magnetic lens 2160, and quadrupole magnets2170 combine to alter the initial electron vectors into parallel vectorswith a decreased cross-sectional area having a substantially parallelpath, referred to as the accelerated electrons 2150. The process allowsthe X-ray generation device 2100 to operate at a lower temperature.Particularly, instead of using a cathode that is the size of theelectron beam needed, a larger electrode is used and the resultingelectrons 2120 are focused and/or concentrated into the requiredelectron beam needed. As lifetime is roughly an inverse of currentdensity, the concentration of the current density results in a largerlifetime of the X-ray generation device. A specific example is providedfor clarity. If the cathode has a 15 mm radius or d₁ is about 30 mm,then the area (π r²) is about 225 mm² times pi. If the concentration ofthe electrons achieves a radius of 5 mm or d₂ is about 10 mm, then thearea (π r²) is about 25 mm² times pi. The ratio of the two areas isabout 9 (225π/25π). Thus, there is about 9 times less density of currentat the larger cathode compared to the traditional cathode having an areaof the desired electron beam. Hence, the lifetime of the larger cathodeapproximates 9 times the lifetime of the traditional cathode, though theactual current through the larger cathode and traditional cathode isabout the same. Preferably, the area of the cathode 2110 is about 2, 4,6, 8, 10, 15, 20, or 25 times that of the cross-sectional area of thesubstantially parallel electron beam 2150.

In another embodiment of the invention, the quadrupole magnets 2170result in an oblong cross-sectional shape of the electron beam 2150. Aprojection of the oblong cross-sectional shape of the electron beam 2150onto the X-ray generation source 2148 results in an X-ray beam that hasa small spot in cross-sectional view, which is preferably substantiallycircular in cross-sectional shape, that is then passed through thepatient 1930. The small spot is used to yield an X-ray having enhancedresolution at the patient.

Referring now to FIG. 22, in one embodiment, an X-ray is generated closeto, but not in, the proton beam path. A proton beam therapy system andan X-ray system combination 2200 is illustrated in FIG. 22. The protonbeam therapy system has a proton beam 268 in a transport system afterthe Lamberson extraction magnet 292 of the synchrotron 130. The protonbeam is directed by the scanning/targeting/delivery system 140 to atumor 1920 of a patient 1930. The X-ray system 2205 includes an electronbeam source 2105 generating an electron beam 2150. The electron beam isdirected to an X-ray generation source 2148, such as a piece oftungsten. Preferably, the tungsten X-ray source is located about 1, 2,3, 5, 10, 15, or 20 millimeters from the proton beam path 268. When theelectron beam 2150 hits the tungsten, X-rays are generated in alldirections. X-rays are blocked with a port 2262 and are selected for anX-ray beam path 2270. The X-ray beam path 2270 and proton beam path 268run substantially in parallel as they progress to the tumor 1920. Thedistance between the X-ray beam path 2270 and proton beam path 269preferably diminishes to near zero and/or the X-ray beam path 2270 andproton beam path 269 overlap by the time they reach the tumor 1920.Simple geometry shows this to be the case given the long distance, of atleast a meter, between the tungsten and the tumor 1920. The distance isillustrated as a gap 2280 in FIG. 22. The X-rays are detected at anX-ray detector 2290, which is used to form an image of the tumor 1920and/or position of the patient 1930.

As a whole, the system generates an X-ray beam that lies insubstantially the same path as the proton therapy beam. The X-ray beamis generated by striking a tungsten or equivalent material with anelectron beam. The X-ray generation source is located proximate to theproton beam path. Geometry of the incident electrons, geometry of theX-ray generation material, and/or geometry of the X-ray beam blocker 262yield an X-ray beam that runs either in substantially in parallel withthe proton beam or results in an X-ray beam path that starts proximatethe proton beam path an expands to cover and transmit through a tumorcross-sectional area to strike an X-ray detector array or film allowingimaging of the tumor from a direction and alignment of the protontherapy beam. The X-ray image is then used to control the chargedparticle beam path to accurately and precisely target the tumor, and/oris used in system verification and validation.

Referring now to FIG. 23, additional geometry of the electron beam path2150 and X-ray beam path 2270 is illustrated. Particularly, the electronbeam 2150 is shown as an expanded electron beam path 2152, 2154. Also,the X-ray beam path 2270 is shown as an expanded X-ray beam path 2272,2274.

Patient Immobilization

Accurate and precise delivery of a proton beam to a tumor of a patientrequires: (1) positioning control of the proton beam and (2) positioningcontrol of the patient. As described, supra, the proton beam iscontrolled using algorithms and magnetic fields to a diameter of about0.5, 1, or 2 millimeters. This section addresses partial immobilization,restraint, and/or alignment of the patient to insure the tightlycontrolled proton beam efficiently hits a target tumor and notsurrounding healthy tissue as a result of patient movement.

In this section an x-, y-, and z-axes coordinate system and rotationaxis is used to describe the orientation of the patient relative to theproton beam. The z-axis represent travel of the proton beam, such as thedepth of the proton beam into the patient. When looking at the patientdown the z-axis of travel of the proton beam, the x-axis refers tomoving left or right across the patient and the y-axis refers tomovement up or down the patient. A first rotation axis is rotation ofthe patient about the y-axis and is referred to herein as a rotationaxis, bottom unit 1912 rotation axis, or y-axis of rotation. Inaddition, tilt is rotation about the x-axis, yaw is rotation about they-axis, and roll is rotation about the z-axis. In this coordinatesystem, the proton beam path 269 optionally runs in any direction. As anillustrative matter, the proton beam path running through a treatmentroom is described as running horizontally through the treatment room.

In this section, three examples of positioning systems 2400 areprovided: (1) a semi-vertical partial immobilization system; (2) asitting partial immobilization system; and (3) a laying position.Elements described for one immobilization system apply to otherimmobilization systems with small changes. For example, a head rest willadjust along one axis for a reclined position, along a second axis for aseated position, and along a third axis for a laying position. However,the headrest itself is similar for each immobilization position.

Vertical Patient Positioning/Immobilization

The semi-vertical patient positioning system is preferably used inconjunction with proton therapy of tumors in the torso. The patientpositioning and/or immobilization system controls and/or restrictsmovement of the patient during proton beam therapy. In a first partialimmobilization embodiment, the patient is positioned in a semi-verticalposition in a proton beam therapy system. As illustrated, the patient isreclining at an angle alpha, α, about 45 degrees off of the y-axis asdefined by an axis running from head to foot of the patient. Moregenerally, the patient is optionally completely standing in a verticalposition of zero degrees off the of y-axis or is in a semi-verticalposition alpha that is reclined about 5, 10, 15, 20, 25, 30, 35, 40, 45,50, 55, 60, or 65 degrees off of the y-axis toward the z-axis.

Patient positioning constraints are used to maintain the patient in atreatment position, including one or more of: a seat support, a backsupport, a head support, an arm support, a knee support, and a footsupport. The constraints are optionally and independently rigid orsemi-rigid. Examples of a semi-rigid material include a high or lowdensity foam or a visco-elastic foam. For example the foot support ispreferably rigid and the back support is preferably semi-rigid, such asa high density foam material. One or more of the positioning constraintsare movable and/or under computer control for rapid positioning and/orimmobilization of the patient. For example, the seat support isadjustable along a seat adjustment axis, which is preferably the y-axis;the back support is adjustable along a back support axis, which ispreferably dominated by z-axis movement with a y-axis element; the headsupport is adjustable along a head support axis, which is preferablydominated by z-axis movement with a y-axis element; the arm support isadjustable along an arm support axis, which is preferably dominated byz-axis movement with a y-axis element; the knee support is adjustablealong a knee support axis, which is preferably dominated by y-axismovement with a z-axis element; and the foot support is adjustable alonga foot support axis, which is preferably dominated by y-axis movementwith a z-axis element.

If the patient is not facing the incoming proton beam, then thedescription of movements of support elements along the axes change, butthe immobilization elements are the same.

An optional camera is used with the patient immobilization system. Thecamera views the subject creating an video image. The image is providedto one or more operators of the charged particle beam system and allowsthe operators a safety mechanism for determining if the subject hasmoved or desires to terminate the proton therapy treatment procedure.Based on the video image, the operators optionally suspend or terminatethe proton therapy procedure. For example, if the operator observes viathe video image that the subject is moving, then the operator has theoption to terminate or suspend the proton therapy procedure.

An optional video display is provided to the patient. The video displayoptionally presents to the patient any of: operator instructions, systeminstructions, status of treatment, or entertainment.

Motors for positioning the constraints, the camera, and video displayare preferably mounted above or below the proton path.

Respiration control is optionally performed by using the video display.As the patient breathes, internal and external structures of the bodymove in both absolute terms and in relative terms. For example, theoutside of the chest cavity and internal organs both have absolute moveswith a breath. In addition, the relative position of an internal organrelative to another body component, such as an outer region of the body,a bone, support structure, or another organ, moves with each breath.Hence, for more accurate and precise tumor targeting, the proton beam ispreferably delivered at point a in time where the position of theinternal structure or tumor is well defined, such as at the bottom ofeach breath.

The video display is used to help coordinate the proton beam deliverywith the patient's breathing cycle. For example, the video displayoptionally displays to the patient a command, such as a hold breathstatement, a breathe statement, a countdown indicating when a breathwill next need to be held, or a countdown until respiration may resume.

Sitting Patient Positioning/Immobilization

In a second partial immobilization embodiment, the patient is partiallyrestrained in a seated position. The sitting restraint system hassupport structures that are similar to the support structures used inthe semi-vertical positioning system, described supra with the exceptionthat the seat support is replaced by a chair and the knee support is notrequired. The seated restraint system generally retains the adjustablesupport, rotation about the y-axis, camera, video, and breath controlparameters described in the semi-vertical embodiment, described supra.

Referring now to FIG. 24, a particular example of a sitting patientsemi-immobilization system is provided. The sitting system is preferablyused for treatment of head and neck tumors. As illustrated, the patientis positioned in a seated position on a chair 2410 for particle therapy.The patient is further immobilized using any of the: the head support2440, the back support 2430, a hand support 2420, the knee support 2460,and the foot support 2470. The supports 2440, 2430, 2420, 2460, 2470preferably have respective axes of adjustment 2442, 2432, 2422, 2462,2472 as illustrated. The chair 2410 is either readily removed to allowfor use of a different patient constraint system or adapts to a newpatient position, such as the semi-vertical system.

Laying Patient Positioning/Immobilization

In a third partial immobilization embodiment, the patient is partiallyrestrained in a laying position. The laying restraint system has supportstructures that are similar to the support structures used in thesitting positioning system and semi-vertical positioning system,described supra. In the laying position, optional restraint, support, orpartial immobilization elements include one or more of: the head supportand the back, hip, and shoulder support. The supports preferably haverespective axes of adjustment that are rotated as appropriate for alaying position of the patient. The laying position restraint systemgenerally retains the adjustable supports, rotation about the y-axis,camera, video, and breath control parameters described in thesemi-vertical embodiment, described supra.

If the patient is very sick, such as the patient has trouble standingfor a period of about one to three minutes required for treatment, thenbeing in a partially supported system can result in some movement of thepatient due to muscle strain. In this and similar situations, treatmentof a patient in a laying position on a support table is preferentiallyused. The support table has a horizontal platform to support the bulk ofthe weight of the patient. Preferably, the horizontal platform isdetachable from a treatment platform

Additionally, leg support and/or arm support elements are optionallyadded to raise, respectively, an arm or leg out of the proton beam path269 for treatment of a tumor in the torso or to move an arm or leg intothe proton beam path 269 for treatment of a tumor in the arm or leg.This increases proton delivery efficiency, as described infra.

In a laying positioning system, the patient is positioned on a platform,which has a substantially horizontal portion for supporting the weightof the body in a horizontal position. Optional hand grips are used,described infra. One or more leg support elements are used to positionthe patient's leg. A leg support element is preferably adjustable alongat least one leg adjustment axis or along an arc to position the leginto the proton beam path 269 or to remove the leg from the proton beampath 269, as described infra. An arm support element is preferablyadjustable along at least one arm adjustment axis or along an arc toposition the arm into the proton beam path 269 or to remove the arm fromthe proton beam path 269, as described infra. Both the leg support andarm support elements are optional.

Preferably, the patient is positioned on the platform in an area or roomoutside of the proton beam path 269 and is wheeled or slid into thetreatment room or proton beam path area. For example, the patient iswheeled into the treatment room on a gurney where the top of the gurney,which is the platform, detaches and is positioned onto a table. Theplatform is preferably lifted onto the table or slid onto the table sothat the gurney or bed need not be lifted onto the table.

The semi-vertical patient positioning system and sitting patientpositioning system are preferentially used to treatment of tumors in thehead or torso due to efficiency. The semi-vertical patient positioningsystem, sitting patient positioning system, and laying patientpositioning system are all usable for treatment of tumors in thepatient's limbs.

Support System Elements

Positioning constraints include all elements used to position thepatient, such as those described in the semi-vertical positioningsystem, sitting positioning system, and laying positioning system.Preferably, positioning constraints or support system elements arealigned in positions that do not impede or overlap the proton beam path269. However, in some instances the positioning constraints are in theproton beam path 269 during at least part of the time of treatment ofthe patient. For instance, a positioning constraint element may residein the proton beam path 269 during part of a time period where thepatient is rotated about the y-axis during treatment. In cases or timeperiods that the positioning constraints or support system elements arein the proton beam path, then an upward adjustment of proton beam energyis preferably applied that increases the proton beam energy to offsetthe positioning constraint element impedance of the proton beam. Thistime period and energy are optionally controlled as a function ofrotational orientation of the patient. In one case, the proton beamenergy is increased by a separate measure of the positioning constraintelement impedance determined during a reference scan of the positioningconstraint system element or set of reference scans of the positioningconstraint element as a function of rotation about the y-axis.

For clarity, the positioning constraints or support system elements areherein described relative to the semi-vertical positioning system;however, the positioning elements and descriptive x-, y-, and z-axes areadjustable to fit any coordinate system, to the sitting positioningsystem, or the laying positioning system.

An example of a head support system is described to support, align,and/or restrict movement of a human head. The head support systempreferably has several head support elements including any of: a back ofhead support, a right of head alignment element, and a left of headalignment element. The back of head support element is preferably curvedto fit the head and is optionally adjustable along a head support axis,such as along the z-axis. Further, the head supports, like the otherpatient positioning constraints, is preferably made of a semi-rigidmaterial, such as a low or high density foam, and has an optionalcovering, such as a plastic or leather. The right of head alignmentelement and left of head alignment elements or head alignment elements,are primarily used to semi-constrain movement of the head. The headalignment elements are preferably padded and flat, but optionally have aradius of curvature to fit the side of the head. The right and left headalignment elements are preferably respectively movable along translationaxes to make contact with the sides of the head. Restricted movement ofthe head during proton therapy is important when targeting and treatingtumors in the head or neck. The head alignment elements and the back ofhead support element combine to restrict tilt, rotation or yaw, rolland/or position of the head in the x-, y-, z-axes coordinate system.

Referring now to FIG. 25 another example of a head support system isdescribed for positioning and/or restricting movement of a human head1902 during proton therapy of a solid tumor in the head or neck. In thissystem, the head is restrained using 1, 2, 3, 4, or more straps orbelts, which are preferably connected or replaceably connected to a backof head support element 2510. In the example illustrated, a first strap2520 pulls or positions the forehead to the head support element 2510,such as by running predominantly along the z-axis. Preferably a secondstrap 2530 works in conjunction with the first strap 2520 to prevent thehead from undergoing tilt, yaw, roll or moving in terms of translationalmovement on the x-, y-, and z-axes coordinate system. The second strap2530 is preferably attached or replaceable attached to the first strap2520 at or about: (1) a forehead position 2532; (2) at a point on one orboth sides of the head 2534; and/or (3) at a position about the supportelement 2536. A third strap 2540 preferably orientates the chin of thesubject relative to the support element 2510 by running dominantly alongthe z-axis. A fourth strap 2550 preferably runs along a predominantly y-and z-axes to hold the chin relative to the head support element 2510and/or proton beam path. The third 2540 strap preferably is attached toor is replaceably attached to the fourth strap 2550 during use at orabout the patient's chin position 2542. The second strap 2530 optionallyconnects to the fourth strap 2550 at or about the support element 2510.The four straps 2520, 2530, 2540, 2550 are illustrative in pathway andinterconnection. Any of the straps optionally hold the head alongdifferent paths around the head and connect to each other in separatefashion. Naturally, a given strap preferably runs around the head andnot just on one side of the head. Any of the straps 2520, 2530, 2540,and 2550 are optionally used independently or in combinations orpermutations with the other straps. The straps are optionally indirectlyconnected to each other via a support element, such as the head supportelement 2510. The straps are optionally attached to the head supportelement 2510 using hook and loop technology, a buckle, or fastener.Generally, the straps combine to control position, front-to-backmovement of the head, side-to-side movement of the head, tilt, yaw,roll, and/or translational position of the head.

The straps are preferably of known impedence to proton transmissionallowing a calculation of peak energy release along the z-axis to becalculated, such as an adjustment to the Bragg peak is made based on theslowing tendency of the straps to proton transport.

Referring now to FIG. 26, still another example of a head support system2440 is described. The head support 2440 is preferably curved to fit astandard or child sized head. The head support 2440 is optionallyadjustable along a head support axis 2442. Further, the head supports,like the other patient positioning constraints, is preferably made of asemi-rigid material, such as a low or high density foam, and has anoptional covering, such as a plastic or leather.

Elements of the above described head support, head positioning, and headimmobilization systems are optionally used separately or in combination.

Still referring to FIG. 26, an example of the arm support 2420 isfurther described. The arm support preferably has a left hand grip 2610and a right hand grip 2620 used for aligning the upper body of thepatient 1930 through the action of the patient 1930 gripping the leftand right hand grips 2610, 2620 with the patient's hands 1934. The leftand right hand grips 2610, 2620 are preferably connected to the armsupport 2420 that supports the mass of the patient's arms. The left andright hand grips 2610, 2620 are preferably constructed using asemi-rigid material. The left and right hand grips 2610, 2620 areoptionally molded to the patient's hands to aid in alignment. The leftand right hand grips optionally have electrodes, as described supra.

Positioning System Computer Control

One or more of the patient positioning unit components and/or one ofmore of the patient positioning constraints are preferably undercomputer control, where the computer control positioning devices, suchas via a series of motors and drives, to reproducibly position thepatient. For example, the patient is initially positioned andconstrained by the patient positioning constraints. The position of eachof the patient positioning constraints is recorded and saved by the maincontroller 110, by a sub-controller or the main controller 110, or by aseparate computer controller. Then, medical devices are used to locatethe tumor 1920 in the patient 1930 while the patient is in theorientation of final treatment. The imaging system 170 includes one ormore of: MRI's, X-rays, CT's, proton beam tomography, and the like. Timeoptionally passes at this point where images from the imaging system 170are analyzed and a proton therapy treatment plan is devised. The patientmay exit the constraint system during this time period, which may beminutes, hours, or days. Upon return of the patient to the patientpositioning unit, the computer can return the patient positioningconstraints to the recorded positions. This system allows for rapidrepositioning of the patient to the position used during imaging anddevelopment of the treatment plan, which minimizes setup time of patientpositioning and maximizes time that the charged particle beam system 100is used for cancer treatment.

Proton Delivery Efficiency

A Bragg peak energy profile shows that protons deliver their energyacross the entire length of the body penetrated by the proton up to amaximum penetration depth. As a result, energy is being delivered tohealthy tissue, bone, and other body constituents before the proton beamhits the tumor. It follows that the shorter the pathlength in the bodyprior to the tumor, the higher the efficiency of proton deliveryefficiency, where proton delivery efficiency is a measure of how muchenergy is delivered to the tumor relative to healthy portions of thepatient. Examples of proton delivery efficiency include: (1) a ratioproton energy delivered the tumor and proton energy delivered tonon-tumor tissue; (2) pathlength of protons in the tumor versuspathlength in the non-tumor tissue; and (3) damage to a tumor comparedto damage to healthy body parts. Any of these measures are optionallyweighted by damage to sensitive tissue, such as a nervous systemelement, heart, brain, or other organ. To illustrate, for a patient in alaying position where the patient is rotated about the y-axis duringtreatment, a tumor near the hear would at times be treated with protonsrunning through the head-to-heart path, leg-to-heart path, orhip-to-heart path, which are all inefficient compared to a patient in asitting or semi-vertical position where the protons are all deliveredthrough a shorter chest-to-heart; side-of-body-to-heart, orback-to-heart path. Particularly, compared to a laying position, using asitting or semi-vertical position of the patient, a shorter pathlengththrough the body to a tumor is provided to a tumor located in the torsoor head, which is a higher or better proton delivery efficiency.

Herein proton delivery efficiency is separately described from the timeefficiency or synchrotron use efficiency, which is a fraction of timethat the charged particle beam apparatus is in operation.

Patient Placement

Preferably, the patient 1930 is aligned in the proton beam path 269 in aprecise and accurate manner. Several placement systems are described.The patient placement systems are described using the laying positioningsystem, but are equally applicable to the semi-vertical and sittingpositioning systems.

In a first placement system, the patient is positioned in a knownlocation relative to the platform. For example, one or more of thepositioning constraints position the patient in a precise and/oraccurate location on the platform. Optionally, a placement constraintelement connected or replaceably connected to the platform is used toposition the patient on the platform. The placement constraintelement(s) is used to position any position of the patient, such as ahand, limb, head, or torso element.

In a second placement system, one or more positioning constraints orsupport element, such as the platform, is aligned versus an element inthe patient treatment room. Essentially a lock and key system isoptionally used, where a lock fits a key. The lock and key elementscombine to locate the patient relative to the proton beam path 269 interms of any of the x-, y-, and z-position, tilt, yaw, and roll.Essentially the lock is a first registration element and the key is asecond registration element fitting into, adjacent to, or with the firstregistration element to fix the patient location and/or a supportelement location relative to the proton beam path 269. Examples of aregistration element include any of a mechanical element, such as amechanical stop, and an electrical connection indicating relativeposition or contact.

In a third placement system, the imaging system, described supra, isused to determine where the patient is relative to the proton beam path269 or relative to an imaging marker placed in an support element orstructure holding the patient, such as in the platform. When using theimaging system, such as an X-ray imaging system, then the firstplacement system or positioning constraints minimize patient movementonce the imaging system determines location of the subject. Similarly,when using the imaging system, such as an X-ray imaging system, then thefirst placement system and/or second positioning system provide a crudeposition of the patient relative to the proton beam path 269 and theimaging system subsequently determines a fine position of the patientrelative to the proton beam path 269.

Monitoring Respiration

Preferably, the patient's respiration pattern is monitored. When asubject, also referred to herein as a patient, is breathing manyportions of the body move with each breath. For example, when a subjectbreathes the lungs move as do relative positions of organs within thebody, such as the stomach, kidneys, liver, chest muscles, skin, heart,and lungs. Generally, most or all parts of the torso move with eachbreath. Indeed, the inventors have recognized that in addition to motionof the torso with each breath, various motion also exists in the headand limbs with each breath. Motion is to be considered in delivery of aproton dose to the body as the protons are preferentially delivered tothe tumor and not to surrounding tissue. Motion thus results in anambiguity in where the tumor resides relative to the beam path. Topartially overcome this concern, protons are preferentially delivered atthe same point in each of a series of breathing cycles.

Initially a rhythmic pattern of breathing of a subject is determined.The cycle is observed or measured. For example, a proton beam operatorcan observe when a subject is breathing or is between breaths and cantime the delivery of the protons to a given period of each breath.Alternatively, the subject is told to inhale, exhale, and/or hold theirbreath and the protons are delivered during the commanded time period.

Preferably, one or more sensors are used to determine the respirationcycle of the individual. Two examples of a breath monitoring system areprovided: (1) a thermal monitoring system and (2) a force monitoringsystem.

Referring again to FIG. 25, an example of the thermal breath monitoringsystem is provided. In the thermal breath monitoring system, a sensor isplaced by the nose and/or mouth of the patient. As the jaw of thepatient is optionally constrained, as described supra, the thermalbreath monitoring system is preferably placed by the patient's noseexhalation path. To avoid steric interference of the thermal sensorsystem components with proton therapy, the thermal breath monitoringsystem is preferably used when treating a tumor not located in the heador neck, such as a when treating a tumor in the torso or limbs. In thethermal monitoring system, a first thermal resistor 2570 is used tomonitor the patient's breathing cycle and/or location in the patient'sbreathing cycle. Preferably, the first thermal resistor 2570 is placedby the patient's nose, such that the patient exhaling through their noseonto the first thermal resistor 2570 warms the first thermal resistor2570 indicating an exhale. Preferably, a second thermal resistor 2560operates as an environmental temperature sensor. The second thermalresistor 2560 is preferably placed out of the exhalation path of thepatient but in the same local room environment as the first thermalresistor 2570. Generated signal, such as current from the thermalresistors 2570, 2560, is preferably converted to voltage andcommunicated with the main controller 110 or a sub-controller of themain controller. Preferably, the second thermal resistor 2560 is used toadjust for the environmental temperature fluctuation that is part of asignal of the first thermal resistor 2570, such as by calculating adifference between the values of the thermal resistors 2570, 2560 toyield a more accurate reading of the patient's breathing cycle.

Referring again to FIG. 24, an example of the force/pressure breathmonitoring system is provided. In the force breath monitoring system, asensor is placed by the torso. To avoid steric interference of the forcesensor system components with proton therapy, the force breathmonitoring system is preferably used when treating a tumor located inthe head, neck or limbs. In the force monitoring system, a belt or strap2450 is placed around an area of the patient's torso that expands andcontracts with each breath cycle of the patient. The belt 2450 ispreferably tight about the patient's chest and is flexible. A forcemeter 2452 is attached to the belt and senses the patients breathingpattern. The forces applied to the force meter 2452 correlate withperiods of the breathing cycle. The signals from the force meter 2452are preferably communicated with the main controller 110 or asub-controller of the main controller.

Respiration Control

Once the rhythmic pattern of the subject's breathing is determined, asignal is optionally delivered to the subject to more precisely controlthe breathing frequency. For example, a display screen is placed infront of the subject directing the subject when to hold their breath andwhen to breath. Typically, a breathing control module uses input fromone or more of the breathing sensors. For example, the input is used todetermine when the next breath exhale is to complete. At the bottom ofthe breath, the control module displays a hold breath signal to thesubject, such as on a monitor, via an oral signal, digitized andautomatically generated voice command, or via a visual control signal.Preferably, a display monitor is positioned in front of the subject andthe display monitor displays at least breathing commands to the subject.Typically, the subject is directed to hold their breath for a shortperiod of time, such as about one-half, one, two, or three seconds. Theperiod of time the subject is asked to hold their breath is less thanabout ten seconds. The period of time the breath is held is preferablysynchronized to the delivery time of the proton beam to the tumor, whichis about one-half, one, two, or three seconds. While delivery of theprotons at the bottom of the breath is preferred, protons are optionallydelivered at any point in the breathing cycle, such as upon fullinhalation. Delivery at the top of the breath or when the patient isdirected to inhale deeply and hold their breath by the breathing controlmodule is optionally performed as at the top of the breath the chestcavity is largest and for some tumors the distance between the tumor andsurrounding tissue is maximized or the surrounding tissue is rarefied asa result of the increased volume. Hence, protons hitting surroundingtissue is minimized. Optionally, the display screen tells the subjectwhen they are about to be asked to hold their breath, such as with a 3,2, 1, second countdown so that the subject is aware of the task they areabout to be asked to perform.

Proton Beam Therapy Synchronization with Respiration

A proton delivery control algorithm is used to synchronize delivery ofthe protons to the tumor within a given period of each breath, such asat the top or bottom of a breath when the subject is holding theirbreath. The proton delivery control algorithm is preferably integratedwith the breathing control module. Thus, the proton delivery controlalgorithm knows when the subject is breathing, where in the breath cyclethe subject is, and/or when the subject is holding their breath. Theproton delivery control algorithm controls when protons are injectedand/or inflected into the synchrotron, when an RF signal is applied toinduce an oscillation, as described supra, and when a DC voltage isapplied to extract protons from the synchrotron, as described supra.Typically, the proton delivery control algorithm initiates protoninflection and subsequent RF induced oscillation before the subject isdirected to hold their breath or before the identified period of thebreathing cycle selected for a proton delivery time. In this manner, theproton delivery control algorithm can deliver protons at a selectedperiod of the breathing cycle by simultaneously or nearly simultaneouslydelivering the high DC voltage to the second pair of plates, describedsupra, which results in extraction of the protons from the synchrotronand subsequent delivery to the subject at the selected time point. Sincethe period of acceleration of protons in the synchrotron is constant orknown for a desired energy level of the proton beam, the proton deliverycontrol algorithm is used to set an AC RF signal that matches thebreathing cycle or directed breathing cycle of the subject.

Multi-Field Irradiation

The 3-dimensional scanning system of the proton spot focal point,described supra, is preferably combined with a rotation/raster method.The method includes layer wise tumor irradiation from many directions.During a given irradiation slice, the proton beam energy is continuouslychanged according to the tissue's density in front of the tumor toresult in the beam stopping point, defined by the Bragg peak, to alwaysbe inside the tumor and inside the irradiated slice. The novel methodallows for irradiation from many directions, referred to herein asmulti-field irradiation, to achieve the maximal effective dose at thetumor level while simultaneously significantly reducing possibleside-effects on the surrounding healthy tissues in comparison withexisting methods. Essentially, the multi-field irradiation systemdistributes dose-distribution at tissue depths not yet reaching thetumor.

Although the invention has been described herein with reference tocertain preferred embodiments, one skilled in the art will readilyappreciate that other applications may be substituted for those setforth herein without departing from the spirit and scope of the presentinvention. Accordingly, the invention should only be limited by theClaims included below.

The invention claimed is:
 1. An apparatus for converting a chargedparticle stream into a charged particle beam used in a cancer therapysystem, said apparatus comprising: a negative ion source configured toproduce the charged particle stream in a first partial vacuum section;and a converting foil configured to convert the charged particle streaminto the charged particle beam, the charged particle beam comprising anoppositely signed charge from the charged particle stream, wherein saidconverting foil provides a portion of a vacuum barrier between saidfirst partial vacuum section and a second partial vacuum section in asynchrotron, and wherein a first pump system operates to maintain afirst partial vacuum in said first partial vacuum section.
 2. Theapparatus of claim 1, wherein said first pump system further comprises:a continuously operating turbo molecular pump configured to pump gasmolecules in said first partial vacuum section to a holding volume; apressure sensor configured to monitor pressure in said holding volume;and a pump controller configured to, based on readings from saidpressure sensor, control a semi-continuously operating pump removingcontents from said holding volume to atmosphere.
 3. The apparatus ofclaim 2, further comprising: a second pump system configured to hold avacuum in said second partial vacuum section, wherein pressure in saidfirst partial vacuum section comprises a pressure of less than about0.0001 torr and more than about 0.000001 torr, wherein pressure in saidsecond partial vacuum system comprises a lower pressure of less thanabout 0.000001 torr, wherein said second pump system maintains a lowerpressure in said second partial vacuum section compared to said firstpartial vacuum section as a result of said vacuum barrier, whereinefficiency of cycling the charged particle beam in said synchrotronincreases due to said lower pressure in said synchrotron.
 4. Theapparatus of claim 2, wherein said converting foil comprises: aberyllium carbon film, wherein said film comprises a thickness of aboutthirty to two hundred micrometers.
 5. The apparatus of claim 1, furthercomprising: an ion beam focusing lens, wherein said lens compriseselectric field lines running in said first partial vacuum sectionthrough the charged particle stream, wherein the electric field linesfocus the charged particle stream, said ion beam focusing lens furthercomprising: a first focusing electrode circumferentially surrounding afirst portion of the charged particle stream; a second focusingelectrode comprising metal conductive paths at least partially blockingthe charged particle stream, wherein said first focusing electrode andsaid second focusing electrode comprises opposite charge, wherein firstelectric field lines run between said first focusing electrode and saidsecond focusing electrode, and wherein the charged particle streamencounters first force vectors running up the first electric field linesthat focus the charged particle stream.
 6. The apparatus of claim 5,said ion beam focusing lens further comprising: at least two additionaloppositely charged focusing electrodes circumferentially surrounding asecond portion of the charged particle stream, wherein second electricfield lines run between said at least two additional electrodes, whereinthe charged particle stream encounters second force vectors running upthe second electric field lines that focus the charged particle stream.7. The apparatus of claim 2, wherein said negative ion source comprises:a magnetic material producing a magnetic field loop, wherein themagnetic field loop yields a magnetic barrier between a high temperatureplasma chamber and a low temperature plasma region, wherein saidmagnetic barrier selectively passes elements of plasma in said hightemperature plasma chamber to said low temperature plasma region,wherein low energy electrons interact with atomic hydrogen to createhydrogen anions in said low temperature plasma region; whereinapplication of a high voltage pulse extracts negative ions from saidnegative ion source to form the charged particle stream.
 8. Theapparatus of claim 1, wherein said synchrotron further comprises: anextraction material; at least a one kilovolt direct current fieldapplied across a pair of extraction blades; and a deflector, wherein thecharged particle beam passes through said extraction material resultingin a reduced energy charged particle beam, wherein the reduced energycharged particle beam passes between said pair of extraction blades, andwherein the direct current field redirects the reduced energy chargedparticle beam out of said synchrotron through said deflector, whereinsaid deflector yields an extracted charged particle beam.
 9. Theapparatus of claim 8, further comprising: an X-ray source located withinabout forty millimeters of the extracted charged particle beam, whereinsaid X-ray source maintains a single position both during use of saidX-ray source and during proton therapy with said cancer therapy system.10. The apparatus of claim 8, wherein said cancer therapy system furthercomprises: a rotatable platform configured to rotate during anirradiation period; an immobilization system mounted on said rotatableplatform, wherein said immobilization system restricts tumor motionduring delivery of the extracted charged particle beam, wherein saidrotatable platform rotates to at least ten irradiation positions in lessthan five minutes during tumor irradiation with the extracted chargedparticle beam.
 11. A method for converting a charged particle streaminto a charged particle beam used in a cancer therapy system, saidmethod comprising the steps of: generating the charged particle streamin a first partial vacuum section using a negative ion source;converting the charged particle stream into an oppositely chargedparticle beam with a converting foil; and maintaining a first partialvacuum in said first partial vacuum section with a first pump system,wherein said converting foil provides a portion of a vacuum barrierbetween said first partial vacuum section and a second partial vacuumsection in a synchrotron used in said cancer therapy system.
 12. Themethod of claim 11, further comprising the steps of: continuouslyoperating a turbo molecular pump in said first pump system to pump gasmolecules in said first partial vacuum section to a holding volume;monitoring pressure in said holding volume with a pressure sensor; andbased on readings from said pressure sensor, semi-continuously operatinga second pump to remove contents from said holding volume to atmosphere.13. The apparatus of claim 12, further comprising the step of:maintaining a vacuum in said second partial vacuum section with a secondpump system, wherein pressure in said first partial vacuum sectioncomprises a pressure of less than about 0.0001 torr and more than about0.000001 torr, wherein pressure in said second partial vacuum systemcomprises a lower pressure of less than about 0.000001 torr, whereinsaid second pump system maintains a lower pressure in said secondpartial vacuum section compared to said first partial vacuum section asa result of said vacuum barrier, wherein efficiency of cycling thecharged particle beam in said synchrotron increases due to said lowerpressure in said synchrotron.
 14. The method of claim 11, furthercomprising the steps of: producing a magnetic field loop with a magneticmaterial at least partially located inside said negative ion source,wherein said magnetic field loop yields a magnetic barrier between ahigh temperature plasma chamber and a low temperature plasma region,wherein said magnetic barrier selectively passes elements of plasma insaid high temperature plasma chamber to said low temperature plasmaregion, wherein low energy electrons interact with atomic hydrogen tocreate hydrogen anions in said low temperature plasma region; andapplying a high voltage pulse across said low temperature plasma regionto extract negative ions from said negative ion source to form thecharged particle stream.
 15. The method of claim 11, further comprisingthe steps of: circumferentially surrounding a portion of the chargedparticle stream with a first focusing electrode; providing a secondfocusing electrode, said second focusing electrode comprising metalconductive paths at least partially blocking the charged particlestream, wherein electric field lines run between said first focusingelectrode and said second focusing electrode, and focusing the chargedparticle stream when the charged particle stream encounters forcevectors running along the electric field lines.
 16. The method of claim11, further comprising the steps of: injecting the charged particle beaminto said synchrotron; accelerating the charged particle beam with saidsynchrotron; and extracting the charged particle beam from saidsynchrotron, said step of extracting comprising the steps of:transmitting the charged particle beam through an extraction material,said extraction material yielding a reduced energy charged particlebeam; applying an extraction field of at least five hundred volts acrossa pair of extraction blades; and passing the reduced energy chargedparticle beam between said pair of extraction blades, wherein saidextraction field redirects the reduced energy charged particle as anenergy controlled extracted charged particle beam.
 17. The method ofclaim 16, further comprising the step of: controlling intensity of theenergy controlled extracted charged beam with an intensity controller,wherein said step of controlling comprises the steps of: inputting afeedback signal to said intensity controller, said step of transmittingyielding emitted electrons in the process of the charged particle beamstriking said extraction material, wherein the emitted electrons areconverted to said feedback signal; comparing said feedback signal to anirradiation plan intensity; and adjusting oscillation of the chargedparticle beam with said intensity controller until said feedback signalyields intensity proximate an irradiation plan intensity, wherein saidenergy controlled extracted charged particle beam comprises anindependent intensity control, wherein said intensity comprises a numberof protons traveling in said extracted charged particle beam per unit oftime.
 18. The method of claim 16, further comprising the step of:generating a tumor X-ray image using an X-ray source located within lessthan about one hundred millimeters of the extracted charged particlebeam, wherein said X-ray source maintains a static position during both:use of said X-ray source; and use of the extracted charged particle beamfor tumor therapy.
 19. The method of claim 16, further comprising thesteps of: rotating a rotatable platform of said irradiation deviceduring an irradiation period; providing an immobilization system mountedon said first rotatable platform, wherein said immobilization systemrestricts tumor motion during delivery of the extracted charged particlebeam, irradiating the tumor with said cancer therapy system, whereinsaid rotatable platform rotates to at least ten irradiation positionsduring said step of irradiating.
 20. A method for converting a chargedparticle stream into a charged particle beam used in a cancer therapysystem, said method comprising the steps of: converting the chargedparticle stream into the charged particle beam with a converting foil,the converting foil comprising carbon, wherein the charged particle beamcomprising an oppositely signed charge from the charged particle stream;and maintaining a first partial vacuum in said first partial vacuumsection with a first pump system, wherein said converting foil providesa portion of a vacuum barrier between a source of the charged particlesand a second partial vacuum section in a synchrotron.